Subfa/inlies, Genera, and Subgenera — Recent and Fossil 57 



1931. Spifdliiia (Hartiuann, von Martens), Gekmaix, Moll. Ter. Fluv. France, II, 

 1>. 526. Type probably intended to be Planorhis vorlex (Linn.). As subgenus. 



1931. Anisus (Studer, 1820) Thh^lk, Handbuch, iv teil, p. 480. As genus. 



1931. Anisus (SS) Thiele, op. cit., p. 481. IVpe Planorhis Icucostoma Millet. As sub- 

 genus of A)iisus. 



1931. Spiralinn (Hartmann) Thiele, o\i. cit., p. 481. Type Planorhis vorlex (Linn.). 

 As subgenus of Anisus. 



1934. Anisus Studer, 1820, Pilsbry, Proc. Acad. Nat. Sci., LXXXVI, p. 62. Type 



Helix planorhis Linn, designated by Gray in 1847. As genus. 



1935. Spiralina (Hartmann) von Martens, 1899, Soos, AUat. Kozleni., XXXII, p. 29. 



As subgenus of genus A^iisus. 

 1935. Animis Studer, 1820, Soos, op. cit., p. 29. As genus. 



Subgenus ANISUS SS. 



Ty]:)e Helix spirorhis Linn. 



Shell (plate 77, figs. 20-22, Anisus spirorhis (Linn.), figs. 16-18, A7iisus 

 leucostomus (Millet), fig. 19, Anisus vortex (Linn.) ) discoidal with many 

 tightly coiled whorls very slowly increasing in diameter, all of the whorls 

 visible on both sides of the shell; whorls rounded or with a sharp carina 

 at the periphery; aperture small, rounded or ovate, modified in carinate 

 species by the peripheral carina. 



Animal. Externally resembling that of Planorhis. 



ANATOMICAL CHARACTERISTICS 

 PLATES 6-7 



GENITALIA. Male Organs (plate 6, fig. 12, spirorhis; plate 7, fig. 2, 

 leucostomus; plate 7, fig. 6, septemgijratus) . Seminal vesicle (SV) long, 

 cylindrical, convoluted, about three times the diameter of the ovisperm 

 duct. Sperm duct (SPD) very long and slender (5 mm. in spirorhis, 7 mm. 

 in septemgyratus, 3 mm. in leucostomus, and 4 mm. in vortex). The 

 prostate is long in vortex and septemgyratus and short in spirorhis and 

 leucostomus. The number of diverticula vary correspondingly, in vortex 

 being about sixty, in septemgyratus fifty-seven, in spirorhis about twenty, 

 and in leucostomus over twenty. The diverticula are sac-like, cylindrical, 

 and are placed on a duct separated from the sperm duct which joins the 

 latter some distance above the vagina to form the vas deferens. Cross 

 sections through the oviduct and prostate show the separation of the two 

 ducts (plate 6, fig. 3 vortex, fig. 8 spirorhis). The prostate duct varies in 

 length in the different species. It is about 1 mm. long in spirorhis, but only 

 about 0.2 mm. long in vortex, septemgyratus, and leucostomus. The diver- 

 ticula of the prostate vary in length and diameter as shown in the figures 

 (plate 6, fig. 12; plate 7, figs. 2, 6). The vas deferens is shorter than the 

 sperm duct by about half its length, and, as usual, is a narrow tube. 



The penial complex is greatly elongated in all species of the genus 

 Anisus. It is about 3.5 mm. long in vortex, 2 mm. long in spirorhis and 

 leucostoinus. The preputium is always shorter than the vergic sac, which 

 may be nearly twice as long in vortex as in spirorhis (figs. 1 and 13 on 

 plate 6). The preputium is cylindrical, usually swollen at the upper part. 

 The vergic sac is elongated, pyriform or club-shaped, narrowing greatly in 

 diameter where it joins the preputium. There is one long, narrow retractor 

 nniscle and apparently no supporting muscles. 



