Subfamilies, Genera, and Subgenera — Recent and Fossil 109 



me overlook this structure in my original description. The species is singu- 

 lar from the nearly total absence of umbilicus' (Benson, 1850, p. 352). The 

 shell is treated as dextral (ultradextral). 



Animal. The anatomy of this species is at present unknown. 



Geographical Distribution. Barrackpore, Bengal, India. 



Species Considered as Valid. Trochorbis trochoidcus Benson, the 

 genotype, is the only species assigned to this genus. 



Remarks. In 1850 (p. 352) Benson noted the trochoid form and small 

 umbilicus of Pkuwrbis trochoidcus and in 1855 (p. 126) erected the group 

 Trochorbis for it. This name has l)een overlooked by most writers on 

 Asiatic mollusks. Dall (1906, p. 105) considered Trochorbis a synonym 

 of Secjmentina. In Preston's Fauna of British India (1915, p. 125) the 

 species appears as Planorbis iSegmentina) trochoideus without reference 

 to its use as type of Trochorbis. Germain (1921, p. 175) does not mention 

 the group name proposed by Benson and places the species trochoidcus in 

 the genus Segmentina. Kennard and Woodward (1926, p. 90) consider it 

 an absolute synonym of Segmentina. Trochorbis is not recognized by 

 Annandale and his co-workers in the studies of the mollusk fauna of the 

 Indian Empire. 



Typical Segmentina is not found in eastern Asia, the species previously 

 referred to that genus now being placed in the genus Polypylis of Pilsbry. 

 Trochorbis trochoideus greatly resembles Plartorbis calathus Benson which 

 belongs to the genus Polypylis and from the shell characters appears to 

 be only specifically distinct from calathus, U one can judge from the very 

 excellent figures of both species in Hanley and Theobald, Conchologia 

 Indica, plate 39, figs. 1-3 (calathus) and 4-6 (trochoideus) . 



The species trochoideus has a much smaller shell than calathus and the 

 periphery is more acute. According to Benson, the apertural lamellae are 

 so weak that he overlooked them in his first description of the species. 

 The Asiatic mollusks allied to Segmentina have shown such diversity in 

 anatomical characteristics that until the animal of trochoideus is examined 

 it seems best to treat Trochorbis as a separate genus. Its place, as far as 

 can be judged at present, is near the group of shells called Polypylis, with 

 the internal lamellae far within the aperture. 



Genus PINGIELLA F. C. Baker, New Genus 

 Type Pyramidula (P alula) peipinensi.^ Ping and Yen 



1932. Pyramidula (Patula) peipineiisis Ping and Yen, Bull. Fan Memorial In.st. Biol., 

 Ill, p. 25, figs. 1-3. Wrongly interpreted as a land shell. 



1938. Ani-fu.^ (Hippeutis) peipinenf^is Mori, Mem. Col. Sci., Kvoto Imp. Univ., Ser. B, 

 XIV. Xo. 2, p. 288, plate 14, fig. 6. 



Shell (plate 78, figs. 8-10). Ultradextral, lenticular, flattened, with 

 sharp i^eripheral carina, the last whorl very large and strongly overlapping 

 or clasping the preceding whorls, the base flattened, with a narrow spire 

 dejiression exhibiting all of the whorls, the depression about one third of 

 the diameter of the shell. Aperture without internal lamellae. Major 

 diameter of shell 7.8 mm. to 8.6 mm. The embryonic whorls are pitted. 



Animal. Foot and pneumostome lead color, body yellowish finely 

 mottled with black. Kidney pigmented (from alcoholic specimens). 



