Subfamilies, Genera, and Subgenera — Recent and Fossil 107 



side, but mostly concealed on lower (left) side, the spire depression forming 

 a false umbilicus. The whorls are rounded or at most only subangulate, not 

 sharply carinate. Lips thin. There are no internal barriers or lamellae 

 within the aperture. The embryonic whorls are marked as in other genera 

 of the family. 



The figure of Plajwrbis umbilicalis in Clessin, Conch. Cab., XVII, Taf. 

 15, fig. 6 does not rei)resent that species but is a good representation of the 

 new genus PingicUa F. C. Baker. Germain (1921, p. 177) has called atten- 

 tion to the discrepancy in Clessin's figure and gives good figures of 

 umbilicalis on plate II, figs. 19, 20, and 21. The periphery in these figures 

 is rather well-rounded. The figures in Hanley and Theobald, Conchologia 

 Indica (1876), plate 40, figs. 7, 8, and 9 show the periphery as slightly 

 carinated. Clench' and Beciuaert (1939) give the best figures observed 

 (plate 1, figs. 8, 9, and 10) showing well the slight angulation of the 

 l^eriphery. We can not agree, however, that Helicorbismearnsi Bartsch is 

 a synonym of umbilicalis (see plate 2, figs. 10-12) ; it is too sharply 

 angulated on the j^eriphery. It is evident that the species referred to the 

 subfamily Segmentininae are in need of careful revision. 



Animal. 'The external soft parts generally resemble those of Gyraulus 

 except that the branchial process and the pulmonary siphon are a little 

 better developed' (Annandale and Prashad, 1921, p. 584). 



ANATOMICAL CHARACTERISTICS 



GENITALIA. 'The male genitalia generally approximate to Simroth's 

 Typus I, but differ in details. The vas deferens is very long and coiled. 

 The penis sac is a well-developed ovoidal structure with an elongated 

 tubular preputium in continuation of the sac. The penis is massive with a 

 lateral opening and without anv stylet' (Annandale and Prashad, 1921, 

 p. 585). 



Radula. 'The radula is very minute and the dental formula is approxi- 

 mately 14-12-1-12-14(26-1-26): The central tooth is comparatively large 

 and bicuspid with sharp cusps. The laterals and marginals both have a 

 peculiar twinned structure, and the line of demarcation between the 

 laterals and marginals is not very sharp. The laterals are tricuspid, the 

 central cusp much the largest' (Annandale and Prashad). The radula is 

 figured on page 583 of the work cited (fig. 16B). The teeth are like those 

 of Bathyontphalus and Hippeutis. The twinned nature noted for some of 

 the teeth was not particularly apparent in the radula of Hippeutis com- 

 planatus examined. 



Geographical Distribution. Not clearly known but including eastern 

 and central China and India, the Philippines, and probably other islands 

 off the cast coast of Asia. 



Species Considered as Valid. Just what species may be included in this 

 genus is not definitely known. The following are believed to belong here: 



Helicurbis umbilicalis (Benson) Helicorbis mearnsii^Sirtsch) 



Hclicorbis caenosus (Benson) Helicorbis papyraceus (Benson) 



Geological Distribution. Not ascertained. 



Remarks. The Segmentina-like shells of India and China referred to 

 Hippeutis are apparently not like the type of that genus, Hippeutis com- 

 planatus (Linn.), at least as far as the shells are concerned. Both agree in 



