taxonID	type	description	language	source
03CF9C77FFEBFFF2FD9A70D04E4495DA.taxon	description	Fig. 13 Following his investigations in the USNM, Ockelmann began to apply some of Verrill & Bush’s names to European specimens. The first of these was to identify a species from the Fladen Ground in the North Sea as T. equalis following communications with Alistair McIntyre (McIntyre 1961). However, T. equalis was not included in the British fauna by Tebble (1966) but was listed by Bowden & Heppell (1968). It appears in the Norwegian literature in 1975 (Lande 1975), but the first figures of European specimens were published by Payne & Allen (1991), and illustrations of specimens from the North Sea are in Oliver & Killeen (2002). Comparisons of the shells from NE America, the North Sea and northern Norway show that they share the same characters and in particular the micro-sculpture of the prodissoconch. This has the characteristic “ menorah ” pattern (Fig. 22 A) which Ockelmann did not see. Ockelmann’s map (Fig. 13) shows a discontinuous distribution with a western Atlantic range from New England northwards into the Labrador Sea but absent from the entire east of Greenland. In the east, it ranges from the North Sea into the Kattegat and all along the Norwegian coast into the Barents Sea.	en	Oliver, P. Graham (2025): Kurt Ockelmann’s unpublished studies on the Thyasiridae (Mollusca: Bivalvia) of the North Atlantic, held in the Natural History Museum of Denmark. European Journal of Taxonomy 1007: 239-278, DOI: 10.5852/ejt.2025.1007.3011, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/3011/13511
03CF9C77FFF4FFECFD9171044A4B936D.taxon	description	Fig. 14 For a great many years this species (Fig. 14) was confused with Axinulus croulinensis (Jeffreys, 1847) and was widely recorded as such from the eastern Atlantic from the Bay of Biscay to northern Norway (see Payne & Allen 1991 for details). It was not until Ockelmann formally recognised this species in the British fauna (Ockelmann pers. comm. in Bowden & Heppell 1968: 263) that the name became established in Europe. Lande (1975) recorded this species from Norway and credits Ockelmann with its identification.	en	Oliver, P. Graham (2025): Kurt Ockelmann’s unpublished studies on the Thyasiridae (Mollusca: Bivalvia) of the North Atlantic, held in the Natural History Museum of Denmark. European Journal of Taxonomy 1007: 239-278, DOI: 10.5852/ejt.2025.1007.3011, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/3011/13511
03CF9C77FFF5FFECFDE274924A7F9094.taxon	description	Fig. 15 This species was originally described from off north-eastern USA and was known from high latitudes in the eastern Atlantic as early as 1878 (Sars 1878) (Fig. 15). Records from farther south in Norway appear in Lande (1975) and from Scotland (Blacknell 1973), both noting Ockelmann’s confirmation of identifications.	en	Oliver, P. Graham (2025): Kurt Ockelmann’s unpublished studies on the Thyasiridae (Mollusca: Bivalvia) of the North Atlantic, held in the Natural History Museum of Denmark. European Journal of Taxonomy 1007: 239-278, DOI: 10.5852/ejt.2025.1007.3011, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/3011/13511
03CF9C77FFF5FFE0FDA0732F4A5B9554.taxon	description	Fig. 16 Mendicula pygmaea was described from off the coast of New England and appears in the European literature in Lande (1975), and Høisaeter (1986) recorded it from the coast of Norway between 60 ° and 63 ° N. Ockelmann’s unpublished map (Fig. 16) shows a wide range but sparse distribution across the N Atlantic Ocean. It was listed from the Skagerrak by Wikander (1989) and later was cited from the North Sea oilfields by Oliver & Killeen (2002). Unfortunately, both Ockelmann and Oliver & Killeen had overlooked the fact that the material from the North Sea was not M. pygmaea but was a neglected species of Adontorhina published subsequently by Barry & McCormack (2007) as A. similis. It is most unlike Ockelmann to have overlooked A. similis, but without recourse to the SEM, he probably could not discern the denticulate dorsal margin typical of Adontorhina. Oliver & Killeen (2002) did figure the denticulate margin, but failed to notice the significance taking the M. pygmaea identification for granted. Larval shells (prodissoconchs) Ockelmann was mentored by Gunnar Thorson who postulated Thorson’s rule concerning the relationship of egg size and larval development to latitude. Egg size and larval development can be inferred in bivalves from their prodissoconch size and this was an area of interest for Ockelmann throughout his research. In his thyasirid archive, we find two very detailed plates of the drawings and sizes of prodissoconchs of 20 species of Thyasiridae (Figs 17 – 18). In addition, there are scatter-charts of the length to height ratios of prodissoconchs (Fig. 19), shell size plotted against depth (Fig. 20) and bar charts of bathymetric ranges (Fig. 21). All of these can be related to prodissoconch size and ultimately to Thorson’s rule. Ockelmann would also have been familiar with Rass’s rule which relates to the variation in larval development within a species affected by latitude or temperature (Laptikhovsky 2006). Unfortunately, we only have the drawings and charts in the archive without any written commentary, so we cannot discern how Ockelmann was going to interpret his results. The effort he made in compiling this data was impressive for the charts in Fig. 21 were compiled from 21 252 individual observations on 10 species. This data was probably compiled before 1976, as it includes T. “ frigida ” rather than T. dunbari. By contrast, the legend on his prodissoconch plate cites “ T. “ frigida ” n. sp. = T. dunbari ” so at least the legend was added after 1976. A selection of these images was sent to the author and published in Oliver & Killeen (2002). At the time we (Oliver & Killeen) were puzzled by the faint radial lines indicated on Ockelmann’s drawing of the prodissoconch of T. equalis (Fig. 17: no. 9) for we were unable to see any. In a forthcoming paper on NE Atlantic thyasirids, using scanning electron microscopy, I compare the prodissoconchs of a number of species and will demonstrate that T. equalis has a very distinct arrangement of raised ridges on the apex of the larval shell that I will describe as the “ menorah ” pattern, as they resemble to arms on the Jewish candlestick of that name. Furthermore, far from the smooth appearance inferred by Ockelmann’s drawings, the prodissoconch displays a variety of distinctive microsculptures that can be used to differentiate species (Fig. 22). While Ockelmann’s drawings adequately indicate the sizes of the prodissoconchs, the details are missing, and this would have made it difficult to publish after the establishment of scanning electron microscopy. The living animal Ockelmann was what one terms as a “ whole animal zoologist ” and making observations on living animals in the laboratory was, I believe, a passion of his and is evidenced in other papers of his (e. g., Ockelmann 1964 a, 1965; Ockelmann & Muus 1978). He made observations on the burrowing behaviour of at least 3 species of Thyasiridae, T. flexuosa, T. equalis and what he called M. pygmaea. The latter two were modified from rough sketches and reproduced in Oliver & Killeen (2002). The fully worked up reconstruction for T. flexuosa is reproduced below (Fig. 23) but not in its original size that was portrait A 3. This diagram shows the bivalve living at depth in the sediment with an anterior inhalant tube and the exhalant flow posteriorly into the surrounding sediment. Once buried in this position, the foot probes further into the sediment and makes a network of such tubes (Dando & Southward 1986). I do not know if Ockelmann had an explanation for such behaviour, but he probably thought that pedal feeding was involved where particles of detrital food were brought into the mantle by the foot. It was not until Southward (1986) and Dando & Southward (1986) discovered that the foot was probing into the anoxic zone to supply its commensal chemoautotrophic bacteria with sulphides that the behaviour was truly recognised. This symbiosis of T. flexuosa with chemoautotrophic bacteria was discussed with Ockelmann by Paul Dando (pers. comm.) who recounts here: “ Kurt described using India ink particles to study the flow of water through the pathways and noted that the inhalant tube flow was sometimes reversed, as noted by the dotted arrow line in Fig. 23. He also noted that the bivalve did not pump water from above and from below at the same time. This then made sense, since it avoided chemical oxidation of sulphide by oxygen before either reached the gills. The figure also shows that Ockelmann appreciated the oxidation of the sediment by water drawn down through the inhalant tube. ” Eve Southward (1930 – 2023) (Dando et al. 2024), on 10 June 1986, wrote to Ockelmann asking for his comments on her interpretation of the burrowing behaviour, and urging him to publish his observations and to join a European consortium to apply for funds to further their research. There is no reply in Eve Southwards correspondence file, but Ockelmann did not publish his observations or join a research consortium. This part of his studies included collecting and observing the larvae, their settlement and early life history. Paul Dando also recalls discussing such matters, including Ockelmann’s observations that the larvae of T. flexuosa and T. sarsii (Philippi, 1845) (Philippi 1845 b) were bentho-pelagic and that on settlement, the larvae chose organic-rich areas such as sunken mats of Zostera leaves. Ockelmann observed that, in his laboratory tanks, the young bivalves lived at the surface of the sediment for about a year before burrowing and taking up the life position seen in the above diagram. Paul Dando also recalls Kurt explaining to him how he studied the ciliary currents entering and exiting the mantle cavity by jamming open the valves so that he could see inside. Kathe Jensen (pers. comm.) also recalls Kurt’s enthusiasm for these observations in 1972. This study was aided by Ockelmann’s invention of a detritus sledge for collecting meiobenthos and newly settled larvae (Ockelmann 1964 b). Ciliary currents A routine part of the description of the function of a bivalve is to record the ciliary currents on the mantle and gill as pioneered by Ridewood (1903) and later by Atkins (e. g., 1937). Two diagrams (Fig. 24 A – B) illustrate ciliary currents in the mantle of what appears to be Thyasira flexuosa. The mantle ciliary currents are shown in great detail and would have taken very careful observation to record. This diagram is instructive as it indicates mantle apertures both fixed by tissue fusion and by ciliary junctions. The presence of two posterior apertures has been noted in some species by Payne & Allen (1991) and Zelaya (2009); the former suggested the second (ex a 2 here) was a second inhalant aperture while the latter only recorded their presence. Ockelmann’s diagram clearly shows a small current exiting at ex a 2 and I suggest this is expelling pseudofaeces. It also shows that only the upper exhalant aperture is created by mantle fusion (solid black line) while the other apertures are created by weaker ciliary junctions that most frequently are not preserved in preserved specimens. Figure 24 C shows glandular areas on the mantle in four species and that their extent is different in the four illustrated. The extent of the glandular areas has been shown to be a useful taxonomic character and was cited by Oliver & Killeen (2002). Gross anatomy One assumes that in preparation of the monograph that as each shell was illustrated, so too was the gross anatomy, but only six anatomical diagrams are present in the archive. These are a mixture of stipple drawing and ink, are morphologically exact but stylised interpretations that reflect Ockelmann’s knowledge of the anatomy and mastery of the pen (Fig. 25).	en	Oliver, P. Graham (2025): Kurt Ockelmann’s unpublished studies on the Thyasiridae (Mollusca: Bivalvia) of the North Atlantic, held in the Natural History Museum of Denmark. European Journal of Taxonomy 1007: 239-278, DOI: 10.5852/ejt.2025.1007.3011, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/3011/13511
03CF9C77FFF5FFE0FDA0732F4A5B9554.taxon	discussion	Other shell drawings • Thyasira tortuosa (Jeffreys, 1881) Within the archive, besides the typical stipple drawings, is a rough sketch (Fig. 26 C) of the anatomy of T. tortuosa made from a dried specimen from the French Travailleur expedition of 1880, dredge 10. It might be assumed that Ockelmann was sent this material, for there is no evidence that he visited the Paris museum where the bulk of this collection is kept. However, there are 2 lots in the Smithsonian, USNM 61983 / 61984, which are ex Travailleur in Jeffreys collection and it is likely it was one of these that he drew during his visit in 1959. Lot number USNM 61984 is listed as a lectotype, selected by Ockelmann, in the Smithsonian catalogue, but this was never formally published. By chance, one of these (USNM 61983) was illustrated by Payne & Allen (1991: fig. 45). Ockelmann indicates that the prodissoconch is sculptured and indeed it has a “ menorah ” pattern (Fig. 26 E) as seen in T. equalis (Fig. 22 A); this was not mentioned by Payne & Allen (1995). Also not mentioned by Payne & Allen (1995) and not commented upon by myself is Ockelmann’s observation that the uppermost part of the anterior adductor is separate from the remainder. It is indicated here as a “ separate portion of ant add ” and he also indicated in his anatomical diagram of T. dunbari (Fig. 25 B), where it is annotated as “ SP ”. • Thyasira (Parathyasira) granulosa (Monterosato, 1874) (Fig. 27 A – C) Here, Ockelmann illustrated the typical radially arranged microspicules on the shell surface (Fig. 27 B). These spicules can be seen on the supposed lectotype and paralectotype of Thyasira flexuosa var. rotunda in the Smithsonian, USNM 61942 and 61942 a. This selection was never formally published and is now superceded by the presence of type material from the type locality in the NHMUK. • Thyasira succisa (Jeffreys, 1876) (Fig. 27 D – E) • Axinopsida orbiculata (G. O. Sars, 1878) (Fig. 27 F – G) • Thyasira (Axinulus) brevis (Verrill & Bush, 1898) (Fig. 28 A – B) • Thyasira (Axinulus) croulinensis (Jeffreys, 1847) (Fig. 28 C – D) • Thyasira (Genaxinus) eumyaria (M. Sars, 1870) (Fig. 28 E) • Mendicula ferruginosa (Forbes, 1844) (Fig. 28 F) • Thyasira flexuosa (Montagu, 1803) (Fig. 29 A – C) • Thyasira sarsii (Philippi, 1845 b) (Fig. 29 D – E) • Channelaxinus perplicatus (Salas, 1996) The illustrated shell (Fig. 30 A) is not identified, but is a typical example of what was known as Thyasira plicata (Verrill, 1885) but is now Channelaxinus perplicatus. • Axinus grandis (Verrill & Smith, 1885) The stipple drawing of the hinge of A. grandis is labelled “ holotype ” and is probably one of the shells in the Smithsonian under USNM 44824. There is a little variance in the literature, as Payne & Allen (1991) cite the holotype as being in the MCZ Harvard, the station data is the same for both USNM and MCZ shells.	en	Oliver, P. Graham (2025): Kurt Ockelmann’s unpublished studies on the Thyasiridae (Mollusca: Bivalvia) of the North Atlantic, held in the Natural History Museum of Denmark. European Journal of Taxonomy 1007: 239-278, DOI: 10.5852/ejt.2025.1007.3011, URL: https://europeanjournaloftaxonomy.eu/index.php/ejt/article/download/3011/13511
