142 The Molluscau Family Plauorbidae 



A Helisoma abundantly distributed in California, and believed to be a 

 race of the Mexican Helisoma tenue (Phil.), has been named H. tenue 

 calij orniense by F. C. Baker. The genitalia are shown on plate 32, fig. 1. 

 The seminal vesicle (SV) is wide and long (5 mm.). It swells in the center 

 and tapers at each end. It is made up of many small vesicles. The ovisperm 

 duct is 5.5 mm. long, narrow, and for two-thirds of its length is bordered, 

 on one side only, by many small, rounded vesicles. These are probably part 

 of the seminal vesicle system. The sperm duct (SPD) is 3 mm. long and is 

 very narrow. The prostate is short ( 1.3 mm. long) and wide ( 1 mm.) and has 

 twelve rows of long, club-shaped diverticula (fig. 6, the prostate in section). 

 The vas deferens ( VD) is a long, narrow tube 11 mm. long. The sperma- 

 theca (S) is pyriform, 1.5 mm. long, with a long, narrow duct about 2.5 

 mm. long, enlarged as it enters the long and narrow vagina (VG). The 

 ovotestis is made up of very large, club-shaped diverticula in eleven rows. 



The penial complex (fig. 3) has a large, pyriform preputium 2.2 mm. 

 long and a cylindrical vergic sac 1.5 mm. long. The penial gland (fig. 5) 

 is short and cup-shaped with many vertical folds. Its duct is relatively 

 short (5 mm.). Figure 2 shows the penial complex with the preputium 

 pushed upward, the vergic sac placed at the side. There is a wide, very 

 muscular diaphragm. The verge (fig. 2, V) is wide above but tapers to a 

 narrow point below. Figure 7 shows the penial complex of a specimen from 

 Prospect Park, near Redlands, California. The preputium is pyriform and 

 very wide at the summit. It is 3 mm. long. The verge is 3 mm. in length 

 and is not as pyriform in shape as in the other Californian sjiecimens 

 examined. The gland duct is over twice as long (14 mm.) as in the Shandon 

 specimens. The Prospect Park specimens are very large, which probably 

 accounts for the great length of the duct. There is one large retractor 

 muscle and one or two supporting muscles. 



The genitalia of calij orniense are peculiar in the great length and size 

 of the seminal vesicle, in the very short prostate, and in the sessile 

 penial gland. 



One of the largest of west American planorbids is Helisoma traskii 

 (Lea). The genitalia of this species are shown in fig. 17 on plate 32. The 

 seminal vesicle is shaped like that organ in calif orniense (see fig. 1) and is 

 coiled in much the same manner. It is about 9 mm. long (when extended) 

 and 1 mm. wide and is composed of many small vesicles. The ovisperm 

 duct (SO) is very long (16 mm.) two-thirds of which bears small, widely- 

 spaced vesicles on the lateral margin. The sperm duct is 6 mm. long and 

 0.5 mm. wide for two-thirds of its length and tapers to about half this 

 diameter near the point of contact with the prostate duct. The prostate 

 (PRS) is verv long (6.5 mm.) and about one-fourth as wide as long (1.5 

 mm. wide) . There is a short prostate duct branch at each end of the sperm 

 duct beneath the prostate. In section (fig. 12), the prostate shows fourteen 

 rows of diverticula of varying length, unbranched. In the section, the 

 nidamental gland (NG) is composed of several large diverticula. The vas 

 deferens is a long, narrow tube (25 mm. long). The spcrmatheca (S) is of 

 unusual length (3.5 mm.), is club-shaped and is placed at the end of a 

 very long duct ( 10 mm.) which enlarges at its point of entrance into the 

 short, narrow vagina (VG). The ovotestis (OT) consists of large, club- 

 shaped diverticula of varying length, thirteen rows being counted in a 



