104 The Molluscan Family Planorhidae 



Genus POLYPYLIS Pilsbry, 1906 



Type by original designation Segmentina largillierii 

 (Dunker)(= S. hemisphaerula (Benson) ) 



1906. Polijpylis Pilsbry, Proc. Acad. Nat. Sci. Phil., LVIII, p. 166. Type Segmentina 

 largillierti (Dunker). As subgenus of Segmentina 



1921. Segmentina (part) Prashad (non Fleming), Rec. Ind. Mus., XXII, p. 585. 



Mentions Segmentina calathus (Benson), included in Polypylis 



1922. Segmentina Annandale (non Fleming), Rec. Ind. Mus., XXIV, p. 362. 



Mentions Planorbis calathus Benson and Planorhis caenosus Benson, both 

 included in Polypylis 



1923. Polypylis Germain, Rec. Ind. Mus. XXI, p. 164. As synonym of Segmentina 

 1939. Polypylis Haas, Field Mus. N. H., Zool., Miscel. Notes, XXIV, p. 96, fig. 8a. 



Type Segmentina largillierti (Dunker) (= <S. hemisphaerula (Benson)). As 

 subgenus of Segmentina 



Shell (plate 79, figs. 7-9) less compressed than Segmentina (nitida) and 

 not carinate, but glossy with deeply clasping whorls. The parietal lamina 

 is obliquely transverse, the others transverse, basal long, a shorter one in 

 the outer wall, and one or two in the upper margin. There are several or 

 many barriers (Pilsbry). The embryonic whorls are punctured. 



Animal. Not examined. 



ANATOMICAL CHARACTERISTICS 

 PLATE 5 



GENITALIA. Male Organs (fig. 7) . Seminal vesicle (SV) almost twice 

 the diameter of the ovisperm duct, rather long (2 mm.) convoluted, with 

 but few pustulose excrescences. The vesicle gradually decreases in diam- 

 eter to the ovisperm duct which is not sharply distinguished from the 

 vesicle. Sperm cluct (SPD) about 3 mm. long, rather narrow. Prostate 

 1.3 mm. long, on a separate prostate duet (PD), consisting of twenty-eight 

 to thirty-four long and narrow diverticula, the tip of which is bent over 

 in most of the diverticula (fig. 4). Several of the diverticula are bifid at 

 the end. The free prostate duct is very short. The vas deferens (VD) is a 

 small, tube-like duct somewhat shorter than the sperm duct. 



The penial complex (plate 8, fig. 10) is long and narrow (0.5 mm. long). 

 The preputium (PR) is sac-like, rather narrow and elongated (1 mm. 

 long). The vergic sac (VS) is two-thirds as long as the preputium and is 

 very narrow. There is a single flagellum (FL) which is long (over 1 mm.) 

 and narrow and has a bulbous enlargement at the end which is almost half 

 as long as the flagellum. The narrow part of the flagellum has about the 

 same diameter as the vergic sac. The vas deferens enters the vergic sac 

 at one side of the flagellum, as shown in the small figure in fig. 10. There 

 is one large retractor muscle (RM) which is attached to the preputium 

 near the junction of this organ with the vergic sac. 



In Polypylis calathus there are two short flagella and the vergic sac is 

 longer than in hemisphaerula. The pilasters, also, are very thick pads in 

 calathus. There are over thirty diverticula on the prostate of calathus and 

 the seminal vesicle is very large with projecting vesicles. 



Internally, in the penial complex of hemisphaerula (plate 8, fig. 9) the 

 preputium has two pilasters extending the whole length of the sac. There 

 is a small, narrow muscular ring or diaphragm (D) separating the preputial 



