Peloparion Iredale, 1937

Hyman, Isabel T. & Ponder, Winston F., 2010, A morphological phylogenetic analysis and generic revision of Australian Helicarionidae (Gastropoda: Pulmonata: Stylommatophora), and an assessment of the relationships of the family 2462, Zootaxa 2462 (1), pp. 1-148 : 41-42

Peloparion Iredale, 1937

Peloparion Iredale, 1937c: 8 . Type species Helicarion helenae Godwin-Austen, 1883 (SD Iredale, 1941: 7).

Description. External morphology: Shell reduced, 2.5–2.7 whorls, glossy, spire and apex flattened. Protoconch smooth ( Peloparion iridis ) or sculptured with incised spiral grooves ( P. helenae ); teleoconch smooth. Whorl profile rounded above and below evenly convex periphery. Internal walls of early whorls complete; umbilicus closed. Right mantle lap large, rounded; left mantle lap moderately small, rounded ( P. iridis ) or tapering to a slight point ( P. helenae ); mantle laps fused at base, right mantle lap with dark border around edge and left mantle lap with dark stripe through middle, both laps with dark spots. Mantle lobes small to medium, median and left lobe fused. Sides of body and mantle laps and lobes covered with tiny specks of pale pigment iridescent in life in P. iridis ( P. helenae not examined alive). Caudal apparatus as for genus; caudal foss vertical slit in tail.

Mantle cavity: As for family. Mantle with visible minor blood vessels; pigmentation of white spots.

Digestive system: Oesophageal crop present.

Genital system: As for family. Carrefour and talon both embedded in albumen gland. Free oviduct of medium length; capsular gland present; internal longitudinal pilasters absent. Bursa copulatrix inserted on vagina, short (less than half spermoviduct length) in P.helenae , or moderately short (about half spermoviduct length) in P. iridis ; duct of bursa copulatrix wide ( P. iridis ) or narrow ( P. helenae ), distinguishable from bursa copulatrix, internally with longitudinal pilasters. Vagina internally with longitudinal pilasters. Epiphallus enters penis through simple pore ( P. iridis ) or a medium length verge ( P. helenae ); penis internally smooth ( P. helenae ) or covered in faint longitudinal ridges ( P. iridis ), longitudinal penis pilasters present, circular pilasters also present in P. helenae , diverticulum on penis absent. Penial sheath enclosing only penis; penis retractor muscle attached to epiphallus. Epiphallus simple internally. Epiphallic retractor caecum absent. Flagellum present; flagellum and distal part of epiphallus with small internal cryptae forming external projections ( P. helenae ), or with internal cryptae hidden by a thick external layer of muscle ( P. iridis ). Spermatophore ( P.helenae only) soft capsule with firm tail pipe open at one end, tail pipe moderately long, narrow, sculptured at base of capsule with few short branching spines.

Radula: Relatively long and narrow. Central tooth with small ectocones; mesocone longer than tooth base. Lateral and marginal tooth fields distinguishable. Lateral teeth with endocone smaller than central tooth ectocones; ectocone equal in size to those on central tooth; mesocone shorter than tooth base, or longer than tooth base. Marginal teeth with endocones absent; ectocones approximately same length and breadth as mesocone, subdivided into extra teeth.

Remarks. Peloparion was introduced as a subgenus of Helicarion for Vitrina hyalina Pfeiffer, 1855 (now Mysticarion hyalina ; see above), with Helicarion helenae Godwin-Austen, 1883 as a synonym ( Iredale 1937c). Later Iredale (1941) separated the two species, stated that the new subgenus name had been intended for helenae , not hyalina , and raised it to genus level, as well as describing a second species in the genus, Peloparion submissus Iredale, 1941 . Two species, P. helenae and P. submissus , were recognised by Smith (1992) and Smith et al. (2002). Hyman (2007) recognised that two different species were represented in Godwin-Austen’s (1883b) figures of Helicarion helenae and consequently synonymised H. helenae and P.submissus , and described a new species, Peloparion iridis Hyman, 2007 .

Peloparion helenae and Peloparion iridis were examined for the current study and the genus description below is based on both species. Peloparion iridis was described in detail by Hyman (2007), so that information is not included here.

Members of the genus are distinctive in having small, flattened, reduced shells of fewer than three whorls and a dark border surrounding the rounded mantle laps which are pigmented with dark spots. Specimens in ethanol have tiny specks of pale pigment on the mantle laps and lobes and on the body which are iridescent in living P. iridis (only visible under magnification; P. helenae not examined alive).

Peloparion differs from the other southeast Australian genera ( Helicarion , Mysticarion , Parmavitrina , Brevisentis ) in the shape of the flagellum and the spermatophore, although the latter structure was only observed in P. helenae . A close examination reveals internal cryptae in the flagellum and/or the distal epiphallus in both species, indicating that their spermatophores have spines. However, the cryptae are not visible from the outside of the flagellum, as they are in all the other southeast Australian genera. This is due to the presence of a thick muscular sheath around the flagellum in P. iridis . In P. helenae , it is due to the positioning of the cryptae, which are situated only in the distal end of the epiphallus. This corresponds to the presence of only a few short branching spines on the spermatophore around the base of the tail-pipe. The presence of cryptae, absence of an epiphallic caecum and extremely short vagina unite this genus with the southeast Australian group of helicarionid genera.