Planorbacochlea planorbis ( Hedley, 1924 ) Shea & Colgan & Stanisic, 2012

Shea, M., Colgan, D. J. & Stanisic, J., 2012, 3585, Zootaxa 3585, pp. 1-109 : 50-51

Planorbacochlea planorbis ( Hedley, 1924) n. comb.

( Figs 15G, H; 16G, H; 17G, H; 18F–H; 19G, H; 25C, D; 26C, D; 27H; 28A, B)

Gyrocochlea planorbis Hedley, 1924: 217 .

Gyrocochlea planorbis: Iredale 1937: 323 ; Iredale 1941a: 268; Smith 1992: 191; Stanisic et al. 2010: 198 (in part).

Diagnosis. Shell very small, coppery to orange brown, biconcave with weakly depressed spire. Protoconch sculpture spiral consisting of 24 to 36 prominent, closely spaced, beaded spiral cords and weak, closely spaced radial ridges becoming more pronounced toward the protoconch-teleoconch boundary. Teleoconch sculpture of numerous, prominent, quite uniformly spaced, slightly sinuate, orthocline to opisthocline radial ribs. Ribs on body whorl 75–138. Umbilicus open, U-shaped to wide cup-shaped. Penis club- or pear-shaped with a long tapering distal portion, apically with a scoop-like verge, with a terminal pore and approximately one third length of penis, longitudinal pilasters distally.

Type material examined. Holotype. AM C.233, Port Stephens , NSW . Paratypes. AM C.103620, same data as holotype .

Other material examined. Port Stephens: AM C.368601, AM C.462535, AM C.463729, AM C.464076, AM C.464083. Uffington State Forest: AM C.309904, AM C.309918, AM C.309923. Dungog: AM C.309910. Chichester State Forest: AM C.309908, AM C.309909, AM C.309916. Davis Creek: AM C.309164.

Description. Shell very small, coppery to orange brown, biconcave with weakly depressed spire. Whorls 3.50–4.37, tightly coiled, the last inflated and descending in front. Sutures strongly impressed. Shell diameter 2.87–3.42 mm (mean 3.25 mm), height1.49–2.00 mm (mean 1.76 mm), H/D 0.48–0.54 (mean 0.51). Protoconch of 1–1.25 whorls, diameter 0.37–0.53 mm. Protoconch sculpture spiral consisting of 24 to 36 prominent, closely spaced, beaded spiral cords and weak, closely spaced radial ridges becoming more pronounced toward the protoconch-teleoconch boundary. Teleoconch sculpture of numerous, prominent, quite uniformly spaced, slightly sinuate, orthocline to opisthocline radial ribs. Ribs on body whorl 75–138 (mean 100), width of interstices on the first teleoconch whorl equal to width of four to equal to width of six ribs; on the penultimate whorl equal to width of four to less than six ribs; each rib with two or more overlapping periostracal blades. Interstitial sculpture of prominent microradial ribs and low, weaker microspiral cords forming weak beads at their intersection; number of microradials between ribs on the first teleoconch whorl 6–9; on first quarter of body whorl 7–9; height of microspirals variable. Aperture broadly ovately-lunate. Parietal callus prominent, transparent. Umbilicus open, Ushaped to wide cup-shaped, diameter 0.86–1.25 mm (mean 1.01 mm), D/U 2.98–3.64 (mean 3.31). Based on 29 measured adults.

Reproductive tract with ovotestis containing two clumps of alveoli, with more than two alveolar lobes per clump. Hermaphroditic duct narrow to broad crescent-shaped. Spermatheca with a medium-sized oval bulb. Penial retractor muscle inserting at the junction of the penis and epiphallus. Epiphallus equal or shorter than penis entering penis through a verge. Penis club- or pear-shaped with a long tapering distal portion, apically with a scoop-like verge with a terminal pore and approximately one third length of penis; longitudinal pilasters distally. Vagina shorter than penis. Atrium short.

Distribution and habitat. Port Stephens in the vicinity of Nelson Bay and Shoal Bay, to the upper Hunter Valley near Muswellbrook and the northern foothills of the Hunter Valley between Dungog, Clarencetown and Chichester State Forest, NSW; found in eucalypt forest and dry vine thickets, living under logs and rocks.

Remarks. Planorbacochlea planorbis ( Hedley, 1924) n. comb. has spiral protoconch sculpture somewhat similar to P. graemei from the Lake Macquarie area but is readily distinguished from that species by the greater number of ribs on the teleoconch. In contrast, P. manningensis n. sp., which occurs immediately to the north of P. planorbis in the Manning River drainage, generally has even more crowded ribs on the teleoconch.

Port Stephens P. planorbis have a shell with a less sunken spire and more gradually increasing whorls compared to other specimens of the species with the exception of those from Davis Creek. Shells from sites around Uffington State Forest are smaller in size compared to the coastal Shoal Bay/ Nelson Bay P. planorbis , with fewer whorls and with the last whorl larger and more inflated.The Davis Creek site occurs much further inland than the other P. planorbis sites and no populations are known nearer than Dungog. The aperture is larger in area and ribs appear higher and more widely spaced in Davis Creek P. planorbis than in specimens from the Port Stephens area or from the Uffington State Forest, Marshdale and Main Creek sites.

Anatomically P. planorbis differs from other species in the genus by the internal structure of the penis which exhibits complex transverse pilaster development around the epiphallic entrance and uppermost section of the penis. The anatomy of the verge could only be examined in the Uffington series. There may be a verge present in Port Stephens populations but this could not be determined from the single dissected specimen.

The results of this study demonstrate that the definition of this taxon (as Gyrocochlea planorbis ) given in Stanisic et al. (2010) was very broad and may have encompassed a number of very localised species rather than populations.