Neopyrgoma, Ross & Newman, 2002

Ross, A. & Newman, William A., 2002, A review of the Pyrgoma cancellatum species complex (Cirripedia: Pyrgomatidae), Journal of Natural History 36 (4), pp. 407-421 : 416-417

Neopyrgoma n. gen.

De®nition. Wall single-plated, solid, low conical, not ribbed, margin deeply lobate; basis with arch-like calcareous structures alternating between solid, longitudinal, medially sulcate ribs, terminating between and below marginal lobes of wall.

Type species. Pyrgoma lobata Gray, 1825 , designated herein.

Etymology. Derived from the Greek, neo- new, and - Pyrgoma , little tower, in allusion to its derived structure and aYnities. The gender is neuter.

Remarks. Gray (1825: 102) brie¯y described the wall as`Shell concentrically striated, deeply lobed’ which he diVerentiated from P. cancellatum in having a`. .. shell radiately ribbed’. His description of the operculum is`... conical, four valved, ventral valve [= scutum] linear, posterior valves [= terga] hooked narrow triangular’.

The deeply lobed wall, best described as a torus suspended by ¯ying buttresses, clearly distinguishes this genus from Pyrgoma . The distinction may seem trivial, but in reality it represents a radical innovation that entails considerable modi®cation in growth of the wall and basis. Darwin (1854) did not recognize the arch-like structures forming a considerable part of the basis in Pyrgoma , and therefore he did not appreciate the signi®cance of the deeply lobed margin of the wall in this species. He was also likely misled by his observation that juvenile specimens of P. cancellatum have a wall with the ribs extending beyond the periphery (a characteristic found in essentially all coral-inhabiting barnacles having a ribbed wall).

Neopyrgoma lobata ( Gray, 1825) (®gure 4) P. [yrgoma] lobata Gray, 1825: 102 .

[ Pyrgoma ] lobata: Darwin, 1854: 362 , in part, pl. 12, ®gure 5a.

Creusia rayonnant e Blainville, 1827, pl. 116, ®gure 7a, b.

Diagnosis. Because there is only a single incomplete specimen the diagnosis is the same as for the genus.

Type locality and host. Locality unknown, host not identi®ed.

Type depository. Holotype, Natural History Museum, London, no. 1998.2837.

Remarks. Gray (1825) described brie¯y the wall and operular plates, based on a single specimen (rostro-carinal diameter 10.3 mm), but the opercular plates are not glued to the slab and apparently have been lost. There is a small hole between the wall and basis at the rostral end, through which the opercular plates were evidently removed. Glued to the reverse side of the slab there is a small slip of paper which, in Darwin’s cursive handwriting, reads` P. lobata P. cancellatum’.

We are unable to interpret Gray’s description of the opercular plates. However, it would appear they were somewhat diVerent from those of P. cancellatum . The apical portion of the wall is suVused with rose-pink and the growth ridges are nodose. None of the species of Pyrgoma are known to have a pigmented wall.

After completing our manuscript we had the opportunity to examine a photograph of what is likely this or a related species. The intact wall of this specimen, on Tubastrea micranthus , was collected from Sumilon Island in the Philippine Archipelago (Schuhmacher, in litt.). Inasmuch as Gray (1825) did not cite a locality or host for his species, it is informative to note the presence of Neopyrgoma in the Philippines.