Dictyoropa eurythma ( Hedley, 1924 ) Shea & Colgan & Stanisic, 2012

Shea, M., Colgan, D. J. & Stanisic, J., 2012, 3585, Zootaxa 3585, pp. 1-109 : 81-82

Dictyoropa eurythma ( Hedley, 1924) n. comb.

( Figs 30G; 32G; 34G; 36G; 38F)

Gyrocochlea eurythma Hedley, 1924: 216 .

Gyrocochlea eurythma: Iredale 1937: 323 ; Iredale 1941a: 268; Smith 1992: 191; Stanisic et al. 2010: 200.

Type locality. Northern Rivers (probably between the Brunswick and Tweed Rivers), north-eastern NSW .

Diagnosis. Shell very small, cinnamon brown, spire slightly sunken. Protoconch sculpture reticulate consisting of 15 prominent, widely spaced, broad, continuous spiral cords that intersect with widely spaced radial ridges on the early part of the protoconch forming a lattice; the ridges developing into widely spaced radial ribs on the latter part of the protoconch. Teleoconch sculpture of numerous, prominent, quite uniformly spaced, slightly sinuate, opisthocline radial ribs. Ribs on body whorl 94–146 (mean 120). Umbilicus wide cup-shaped.

Type material examined. Lectotype (here designated). AM C.103618, Northern Rivers , NSW, coll. W. Petterd. Paralectotype. AM C.472889, same data as lectotype .

Other material examined. AM C.63525, labelled as holotype in the collections but not considered to be the type of this species for reasons given below. Not cited by Smith (1992) ; AM C.475920, part of the syntype series but representing an undescribed species .

Description. Shell very small, cinnamon brown, spire slightly sunken. Whorls 3.5–4.25, tightly coiled, the last weakly expanding and descending in front. Sutures strongly impressed. Shell diameter 2.63–3.74 mm (mean 3.18 mm), height 1.28–1.80 mm (mean 1.54 mm), H/D 0.48–0.49 (mean 0.48). Protoconch flat, of 1.12 whorls, diameter 0.50–0.57 mm. Protoconch sculpture reticulate consisting of 15 prominent, widely spaced, broad, continuous spiral cords that intersect with widely spaced radial ridges on the early part of the protoconch forming a lattice; the ridges developing into widely spaced radial ribs on the latter part of the protoconch, here intersected and crossed by much lower spiral cords that form beads at their intersection. Teleoconch sculpture of numerous, prominent, quite uniformly spaced, slightly sinuate, opisthocline radial ribs. Ribs on body whorl 94–146 (mean 120), width of interstices on the first teleoconch whorl greater than or equal to width of six ribs; on the penultimate whorl greater than or equal to width of six ribs; each rib with more than one periostracal blade which overlap. Interstitial sculpture of low prominent microradial ribs and low, weaker microspiral cords forming weak beads at their intersection; number of microradials between ribs on the first teleoconch whorl 8–9; on first quarter of body whorl 7. Aperture broadly ovately-lunate. Parietal callus prominent, transparent. Umbilicus wide cup-shaped, diameter 0.72–1.01 mm (mean 0.91 mm), D/U 3.39–3.64 (mean 3.52). Based on 2 measured adults.

Anatomy unknown.

Remarks. Dictyoropa eurythma ( Hedley, 1924) n. comb. is revised at this time in order to stabilise the nomenclature of the species originally included in Gyrocochlea (see Hedley 1924). A type specimen was never designated for this species. The Australian Museum has a specimen labelled holotype (AM C.63525) but there is a discrepancy between the labelled type and the original description. Hedley’s original description of Gyrocochlea eurythma states that the species has ‘one hundred and ten close, fine radial riblets on the last whorl’. The specimen in the Australian Museum designated as the holotype has a rib count of 146 fine close ribs and therefore is not considered to be the type of the species or part of the type series. Smith (1992) does not cite AM C.63525 as the type but cites a syntype series of 4 specimens (AM C.103618). One of the specimens in this series has a body whorl rib count of 94 (however the end of the body whorl is broken and missing). Most significantly this has a rib count on the first adult whorl of 54 which is exactly the figure given by Hedley (1924). This measurement is considered a more stable character than body whorl rib count and tends to show less variance among species than the latter count (J. Stanisic, personal observation).

Hence, in consideration of the problem with the labelled type in the Australian Museum, and in the absence of any other original material, the syntype mentioned above has been chosen here as lectotype. The type locality (deduced from Petterd material cited by Hedley in relation to other species in that publication) is probably somewhere between the Brunswick and Tweed Rivers, north-eastern NSW.

The specimen chosen as lectotype has reticulate protoconch sculpture ( Fig. 36G). Others in the syntype series ( AM C.475920) have a predominantly crowded spiral sculpture and represent a different genus and species ( Fig. 36H) .