Groups of Uncertain Affinities 193 



the outer marginals indistinct and uncountable (op. cit., p. 871). No men- 

 tion is made of the cusps of the teeth. There seems to be great uniformity 

 in the total number of teeth but some variation in the number of lateral 

 teeth. 



The published information concerning the anatomical details is wholly 

 insufficient for purposes of classification. 



Geographical Distribution. Lake Baikal, Siberia. The different species 

 occur at varying dei)ths, thus maacki occurs at great depths, principally 

 between 150 and 350 meters. Valvatoides, on the other hand, occurs in 

 comparatively shallow water, from two to ten meters. One species is found 

 in the Angara River, near Lake Baikal iamauronicus). Another species is 

 found in Japan ( japonicus) . Westerlund includes Europe, Thessalia, be- 

 tween Greece an^l Turkey, in the distribution of the genus. This range needs 

 confirmation. 



Remarks, The genus Choanoinphalus is a group of mollusks probably 

 related to the Planorbidae but of uncertain status as to its proper position 

 in the classification of the fresh-water pulmonates. Dall (1870) and Tryon 

 (18841 placed the genus, in the subfamily Pompholiginae with Pompholyx 

 {Paraphohjx) and Carrriifex. Crosse and Fischer in 1879 compared the 

 genus with the American group Carinifex and suggested its group relation- 

 ship with the fossil Valvata multiformis { = trochiiormis) . The resemblance 

 to Carinifex in both Choanomphalus and the Steinheim fossil itrochi- 

 formis) is superficial, Choanomphalus not having the same characteristics 

 of anatomy found in Carinifex and Paraphohjx. Westerlund, in 1902 (p. 

 120), placed Choanomphalus in the subfamily Planorbinae. 



In 1909, W. A. Lindholm made a study of the Lake Baikal fauna and 

 divided Choanomphalus into three subgenera, as noted below. 



1. Choanomphahis Sensu Stricto. Type Choanomphalus maacki Gerstfeldt 



2. Achoaiiomphalus Lindholm. Type Choanomphalus amauronius Bourguignat 



3. Sulcifer Lindholm. Type Choanomphalus schrencki W. Dj-bowski 



The Japanese species is placed in a separate section by Lindholm, 

 Choanomphalodes, 1927; type Choanomphalus japonicus Preston. 



Germain (1923) places the group in a subfamily Choanomphalinae. 

 Dybowski and Grachmalicki ( 1925, pp. 819-881 ) , in an exhaustive mono- 

 graph, review all of the species of Choano))iphalus, some twenty-five in 

 number, of which fifteen are considered valid. The peculiar Planorbis para- 

 doxus Sturany, from Lake Ochrida near the city of Ochrida, in European 

 Turkey, is discussed, but its relationship to Choanomphalus is questioned. 

 It has been thought to be related to Choanomphalus by Sturany and other 

 European conchologists. It probably represents another peculiar form of 

 Planorbidae and its anatomy should be examined. 



The suggestion in the foregoing reference (p. 835), that Segmentina 

 may be related to Choanomphalus is obviously erroneous because that 

 genus has been shown to be the type of a distinct subfamily not known to 

 have any affinities with the Baikal Lake group. A form of Segmentina 

 nitida is found in Lake Baikal and is given the name of angarensis by 

 these two authors. 



On pages 877 to 880, Dybowski and Grachmalicki present a new ar- 

 rangement of Choanomphalus which is made a separate family, Wladis- 

 laviidae. Six genera and some twenty-three lesser groups are designated. 



