44 The Molluscan Family Planorbidae 



on the classification of the larger planorbes of Europe and America, in 

 which Planorbis corneus and the American Helisoma species were discussed 

 and the genitalia and radulae figured. The peculiar penial gland of the 

 genus Helisoma was discussed at length. The same author, in 1933, made a 

 study of the peculiar genitalia of Indoplanorbis exustus of India adding 

 some features to the previous paper by Rao. Later, the same author pub- 

 lished short papers placing certain disputed species in their proper generic 

 position, based on their anatomy. Thus, in 1935, Planorbis wmbilicatellus, 

 long thought to be a Gyraulus, was shown to be a member of the genus 

 Menetus and a new subgenus was proposed for Menetus exacuous 

 (Promenetus) . In 1936, Planorbis obstructus was shown to belong in the 

 genus Tropicorbis and the true relationship of Parapholyx was indicated. 



In 1935, A. Soos published a paper on the Planorbidae of Hungary 

 which included good figures of the genitalia of the species inhabiting that 

 country. In 1934, a paper from the pen of H. A. Pilsbry discussed the 

 planorbid fauna of Florida, their genitalia were figured, and a new name 

 {Sem.inolina) was proposed for the group which is not found outside of the 

 Florida peninsula. The classification of other groups, Tropicorbis, Menetus, 

 Carinifex, and Parapholyx was .discussed and a new genus Australorbis 

 was proposed for the large snails inhabiting South America and the West 

 Indies. The European genus Anisus was ably discussed. A new subfamily, 

 Planorbulinae, was established. Characteristic keys to the genera of 

 American Planorbidae were given, based on anatomical features. It is not 

 overstating to say that this paper is the most comprehensive account of 

 the family Planorbidae from a modern standpoint that has yet appeared. 



From the foregoing summary it is plainly obvious that a detailed study 

 of the classification of the family Planorbidae, based on anatomical in- 

 formation, comparable to the methods used by Pilsbry on the land mol- 

 lusks, is still to be prepared. An attempt to supply this deficiency is the 

 purpose of the present work. It is believed that a foundation has been laid 

 upon which to build a natural classification of the fanfily Planorbidae. 



