138 Annals of the South African Museum. 



forward ventrally. The intestine then bends upward and backward, 

 and follows an S- shaped curve to the left of and above the crop and 

 stomach, finally passing forward again into the rectum, which 

 continues to the respiratory opening. 



Liver consisting of two separate divisions of nearly equal size, the 

 stomach lying between them. The anterior division is somewhat 

 flattened, and is divided into three main lobes by the intestinal loops 

 among which it lies. The ducts of these lobes unite to discharge by 

 a single opening into the thin-walled portion of the stomach. The 

 posterior division occupies (with the hermaphrodite gland) the 

 upper whorls of the shell, and discharges by a duct opening into 

 the posterior muscular portion of the stomach. 



Free retractor muscles. Eight and left tentacular retractors 

 separate from each other and from the " tail muscle " nearly to their 

 origin on the columella. Each divides rather far forward into the 

 retractors of the upper and lower tentacles, having first given off 

 branches on its inner side to the anterior part of the foot. Eight 

 upper tentacular retractor passing between the penis and the vagina. 

 Eetractors of lower tentacles (and lips) thicker than usual. Buccal 

 retractor generally united at its origin with the left tentacular 

 retractor, but only for a very short distance excepting in Dorcas ia 

 alexandri var. rotundata; not bifurcating in front, but having a 

 semicircular insertion around the under side of the buccal mass. 

 Buccal protractors consisting of numerous small strands. Penial 

 retractor arising dorsally from the front end of the floor of the lung. 



Reproductive system (text-fig. 2, C, and PI. V., figs. 1-8). 

 Hermaphrodite gland composed of numerous very narrow follicles 

 embedded in the inner side of the posterior division of the liver. 

 Hermaphrodite duct densely convoluted, but usually very slender, 

 though somewhat swollen in Triyoneplirus gypsinus and T. lucanus. 

 Vesicula seminalis long and conspicuous. Albumen gland often very 

 large. Common duct not convoluted or twisted. Free oviduct 

 rather short, much swollen in Trigonephrus, and having irregular 

 longitudinal folds projecting into its cavity. Eeceptaculum seminis, 

 or spermatheca, oval, lying against the left side of the common duct. 

 Eeceptacular duct usually moderately long, always without a diverti- 

 culum. Vagina long, excepting in Trigonephrus fjlobnlus, T. 

 yi/psinus, and T. namaquensis, in which it is rather short and 

 slightly swollen. Genital atrium, or vestibule, extremely short, 

 being scarcely developed at all. 



Penis long and muscular, with internal longitudinal folds. In 

 Trigonephrus these folds are corrugated (PI. IV., figs. 27-29) ; in 



