60 The Molluscan Family Plauorbidae 



The teeth are all very uniform in form. Anisus has fewer teeth in a row 

 than Planorbis, the formula of which is 25-1-25, but the teeth are similar 

 in form and number of cusps. 



For the anatomical information herein presented the following ma- 

 terial has been available, all received from Mr. A. Jankowski, of Warsaw, 

 Poland: 

 vortex, Eight examples from stream in meadow at Jab-Tonna, 18 km. northeast of 



Warsaw, Poland. 

 spirorbis, Eight specimens from a trench in Struga, 12 km. northeast of Warsaw, 



Poland. 

 septemgyratus, Three examples from turfy meadow in Drewnica, 4 km. northeast 



of Warsaw, Poland. 

 leucostomus, Three sj^ecimens from small ponds in Bielany Park, Warsaw, Poland. 



Geographical Distribution. The genus Anisus is distributed throughout 

 Europe from Great Britain to Russia and Siberia and southward to Italy 

 and Algeria. Thus the distribution is about the same as that of Planorbis. 

 One species is reported from China {paravortex). This distribution may 

 be enlarged when other si)ecies arc examined anatomically. 



Species Considered as Valid, The following species are understood to 

 conform to the concept of Anisus. 



Ariisus spirorbis (Linn.) Anisus johanseni (Mozley) 



Anisus vortex (Linn.) Anisus perezi (Dupuy) 



Anisus septemgyratus (Ziegler) Anisus jragilis (Millet) 



Anisus leucostoynus (Millet) Anisus paravortex (Ping and Yen) 



Anisus vorticulus (Troschel) Anisus millcti (Germain) 



Anisus villai (Adami) Anisus charteus (Held.) 



Anisus ressmannianus (West.) Anisus centrogyratus (West.) 

 Anisus compressus (Michaud) 



Geological Distribution. This genus begins about the middle of the 

 Miocene period. 



Remarks. The group of European planorbids under the name Anisus 

 differs from the genus Planorbis notably in the form of the penial complex 

 (compare fig. 4, plate 1, Planorbis, with fig. 10, plate 6, Anisus). In Pla- 

 norbis the vergic sac is only one-fourth as long as the preputium while in 

 Anisus this organ is always longer than the preputium and the verge is 

 long and narrow and bears a stylet at the end, which is absent in Planorbis. 

 The presence of the muscular ring and papilla in Anisus is also another 

 striking difference. The seminal vesicle also differs markedly in the two 

 genera. The shell is always flattened and many-whorled but from the shell 

 alone the two groups could scarcely be separated generically. 



The proper name for the group of European planorbids typified by 

 Planorbis spirorbis, vortex, and leucostomus has been in considerable doubt. 

 The name most commonly found in the literature, used by Germain, 

 Lindholm, Soos, Kennard and Woodward, and others, is Spiralina, a nude 

 name published by Hartmann in 1840. In 1899, von Martens used the 

 name for the European Planorbis vortex and the American Planorbis 

 cultratus and sumichrasti. The last two species are now members of the 

 genus Drepanotrema. Thus the type of Spiralina becomes Planorbis vortex 

 and this species was formally designated the type by Lindholm in 1922 

 (p. 320), and by Kennard and Woodward in 1924 (p. 68). But in 1847 

 Herrmannsen (Ind. Gen. Mai. II, p. 286) listed Spiralina Hartmann in the 

 synonymy of typical Planorbis without comment or question, thus, as 



