Subfamilies, Genera, and Subgenera — Recent and Fossil 61 



H. B. Baker remarks (1930, p. 49) 'effectually clothing and simultaneously 

 killing the name Spiralina.' Thus no subsequent use of this name is per- 

 missible. Dall (1905) used the name Diplodisciis Westerlund and cited 

 Planorbis vortex as type, this being the first species listed. But this name is 

 preoccupied by Diesing in Trematodes. 



In 1934 (Proc. Phil. Acad. Sci., j). 62), Pilsbry revived the early name 

 Anisus Studer, 1820 and gave some very good reasons for accepting this 

 name for the group tyjufied by Planorbis vortex and spirorbis, accepting 

 Gray's subsec^uent designation of Helix spirorbis Linn, as type. In this 

 connection he remarks 



Gray's type designation of 'H. spirorbis' is valid for Anisus only if the identity of 

 spirorbis Studer and spirorbis Linn, is admitted. I see no sufficient reason for doubt- 

 ing it. A more serious question relating to Anisus is whether a generic name is valid 

 when admitted by its author to be for a group formed by the union of two prior 

 genera, and containing nothing else. Unfortunately Opinion 9 of the International 

 Commission on Nomenclature is not explicit on this point, but as Anisus has been 

 widely used it had better be retained. 



Other names have been proposed for this European group and would 

 be available but for previous use in other groups. Spirorbis Swainson, 

 Gyrorbis, Diplodiscus, Wuestia, and Gyrostoma are thus affected, as noted 

 in the list of synonyms of Anisus. 



The writer agrees with Pilsbry that, since the name Anisus has had 

 wide use in the literature it had better be retained for this group, since 

 it was proi:)erly clothed as a genus by Gray in 1847. Anisus is used by 

 Thiele in his Handbuch, 1931. The best interest of nomenclature is served 

 by the use of Anisus rather than by coining a new name. 



Subgenus COSTORBIS Lindholm, 1926 

 Type by original designation Planorbis strauchianus Clessin 



1926. Costorbis Lindholm, Archiv. fiir Mollusk., 58 year. Heft 6, pp. 253, 257. Mono- 

 genot.vpe Planorbis strauchianus Clessin. As subgenus of Anisus. 



193L Costorbis Thiele. Handbuch. V, Teil 2, p. 48L Type A. (C.) strauchianus 

 Clessin. As subgenus of Anisus. 



Shell (plate 76, fig. 3). Differing from Anisus in being heavily trans- 

 versely costate, the body whorl angulated above and below, the aperture 

 ciuadrate. 



Animal. The group is anatomically unknown but the shape of the shell 

 would indicate that it should be grouped with Anisus. 



Geographical Distribution. Russia. 



Species Considered as Valid. The only species definitely referable to 

 this subgenus is A7nsus (Costorbis) strauchianus (Clessin). 



Remarks. It is a question whether this group should be separated from 

 Ani.ms. The shell of strauchiami.s is similar in form to that of Anisus 

 septongyratus, differing principally in the costate sculpture. Clessin's fig- 

 ure (copied from Conch. Cab., XVII, plate 31, fig. 5) is reproduced on 

 plate 76, fig. 3. The original description of the shell appears on page 204 

 of Clessin's work. 



