98 The MoUuscan Family Planorbidae 



Animal. With a short foot, rounded in front, jiointed behind; tentacles 

 fihform, enlarged at the base, the eyes sessile at their inner bases. Edge of 

 mantle thickened. The color of the animal is brownish black much paler 

 when immature. 



ANATOMICAL CHARACTERISTICS 

 PLATES 2 and 3 



GENITALIA. Male Organs (plate 3, fig. 2) . Seminal vesicle sac-like, 

 about three times the diameter of the ovisperm duct with several pro- 

 tuberances near the posterior end. It is about 2 mm. long. Sperm duct long 

 (4.5 mm.) and of small diameter. Prostate moderately long (1.7 mm.) 

 with twenty -two to twenty-five club-shaped diverticula of varying lengths, 

 placed on a separate prostate duct, which joins the sperm duct to form the 

 vas deferens. The free portion of the prostate duct is about 0.7 mm. long 

 and of larger diameter than the sperm duct. In the specimens examined the 

 posterior end of the prostate duct is free of diverticula for about 0.3 nnn. 

 The vas deferens is of medium length (about 3 mm.) and of small diameter. 

 A cross section through the prostate and sperm duct shows the relative 

 position of these parts of the animal (plate 3, fig. 3). 



The penial complex (plate 3, fig. 1) is very long (about 3 mm.). The 

 preputium (PR) occupies half of the length of the complex and is elongate- 

 pyriform in shape, the upper part swollen. The vergic sac (VS) is very 

 long and narrow, almost tube-like, and is as long as the preputium. There 

 are two short, narrow flagella (FL) at the end of the vergic sac at the 

 point of insertion of the vas deferens. There is a single, rather wide 

 retractor muscle, but no supporting muscles. 



Internally (plate 2, fig. 2) the preputium presents some striking fea- 

 tures. There is a single heavy ridge on one side (plate 2, fig. 1) which 

 extends vertically up a large portion of the preputium and is in the nature 

 of a pilaster (PL). This ridge merges into a long, sac-like glandular organ 

 which is reflected toward the base or opening of the preputium (SB). 

 This penial gland has a shallow cup, the bottom of which is paved with 

 small protuberances resembling pavement (plate 2, fig. 3), the fleshy sides 

 rolled upward. In cross section this gland presents the appearance shown in 

 fig. 4 of plate 2. On the right side of the preputium there is a long, very 

 narrow pilaster which extends the whole length of the preputium from 

 the external opening upward to the muscular ring (D) separating the 

 preputium from the vergic sac. The large gland is free from attachment to 

 the wall of the preputium and is connected only with the large left 

 pilaster. 



The verge (V) is long and very narrow. At its distal end it bears a 

 fleshy papilla (plate 2, figs. 5, 6, PA) which is also long and narrow. This 

 papilla is an extension of the verge only from one side, the sperm canal 

 (SC) being in the center of the verge at the end, as shown in the figures. 



Female Organs. The spermatheca (plate 3, fig. 2) is long and sac-like 

 and is attached to the vagina by a long narrow duct which is somewhat 

 longer than the spermatheca. The spermatheca is constricted about midway 

 of its length. The vagina is narrow and about 0.5 mm. in length. The 

 uterus is about twice the diameter of the vagina and is a trifle over 1 mm. 

 in length. The nidamental gland is very long (about 3 mm.), sac-like, and 

 envelops the uterus. The oviduct is about half the diameter of the 



