Planorbacochlea yessabahensis Shea & Colgan & Stanisic 2012, n. sp.

(Figs 20B; 21B; 22B; 23B; 24B; 25F; 26F; 28F)

Gyrocochlea planorbis Hedley, 1924: Stanisic et al., 2010: 198 (in part).

Etymology. Named for Yessabah Caves limestone outcrop where the species is abundant.

Diagnosis. Shell very small, orange-brown, biconcave with a weakly depressed spire. Protoconch sculpture reticulate consisting of 18 to 20 prominent, widely spaced, spiral cords and prominent, widely spaced radial ribs becoming more pronounced toward the protoconch-teleoconch boundary. Teleoconch sculpture of numerous, prominent, quite uniformly spaced, slightly sinuate, orthocline to weakly prosocline radial ribs. Ribs on body whorl 100–135. Umbilicus medium U-shaped. Penis club- or pear-shaped, apically with a verge about equal to or less than half the length of penis, pilasters absent. Verge a bulbous swelling with a lateral slit.

Type material examined. Holotype. AM C.119329, W of Kempsey, Yessabah Caves, Macleay Valley, NSW (31° 5.71´S, 152° 41.33´E), 9.x.1979, coll. J. Stanisic, P.H. Colman. Paratypes. Yessabah Caves: AM C.168684, AM C.339449, AM C.368681, AM C.472887, QMMO19854, QMMO37155, QMMO39994, QMMO56123, same data as holotype.

Other material examined. (All Macleay Valley) Carrai Caves: AM C.121694, AM C.168687. Natural Arch: AM C.168692, AM C.339450. Kempsey area: AM C.139748, AM C.140259, AM C.140428, AM C.154971. Mt Sebastopol: QMMO 37768, QMMO 56008. Block and Tackle Spur: QMMO 56496.

Description. Shell very small, orange-brown, biconcave with weakly depressed spire. Whorls 3.75–4.25, tightly coiled, the last inflated and descending in front. Sutures weakly to strongly impressed. Shell diameter 3.22–3.63 mm (mean 3.40 mm), height 1.64–1.97 mm (mean 1.80 mm), H/D 0.50–0.57 (mean 0.52). Protoconch flat, of 1.12–1.25 whorls, diameter 0.35–0.48 mm. Protoconch sculpture reticulate consisting of 18 to 20 prominent, widely spaced, spiral cords and prominent, widely spaced radial ribs becoming more pronounced toward the protoconch-teleoconch boundary. Teleoconch sculpture of numerous, prominent, quite uniformly spaced, slightly sinuate, orthocline to weakly prosocline radial ribs. Ribs on body whorl 100–135 (mean 119), width of interstices on the first teleoconch whorl equal to width of four to greater than or equal to width of six ribs; on the penultimate whorl equal to width of four to less than six ribs; each rib with one, two or more periostracal blades; overlapping thickenings present. 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 6–11. Aperture broadly ovately-lunate. Parietal callus prominent, transparent. Umbilicus medium U-shaped, diameter 0.80–0.97 mm (mean 0.88 mm), D/U 3.51–4.06 (mean 3.86). Based on 10 measured adults.

Reproductive organs 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 to large oval bulb. Penial retractor muscle inserting at the junction of the penis and epiphallus. Epiphallus longer than half the length of the penis. Penis club- or pear-shaped, apically with a verge approximately equal to or less than half the length of penis, pilasters absent. Verge a bulbous swelling with a lateral slit. Vagina shorter than penis. Atrium short.

Distribution and habitat. Macleay Valley, NSW; found primarily in moist rainforest and vine thicket on limestone karst, but also in areas of moist sclerophyll forest, living on the undersides of limestone talus, logs and timber.

Remark. Planorbocochlea yessabahensis n. sp. has more numerous crowded teleoconch radial ribs and a narrower umbilicus compared to other Planorbocochlea species within its region. Anatomically, the large bulbous verge with its lateral slit is the main character which separates this species from its neighbours.

Material here described as P. yessabahensis was included in ‘ Gyrocochlea ’ planorbis by Stanisic et al. (2010).