Notes on SoutJi African Mollusca. 139 



Dorcasia both the folds and the intervening furrows are covered 

 with diagonal rows of very minute papillae (PI. IV., fig. 30). Penis- 

 papilla absent or quite vestigial. Penial retractor attached to the 

 posterior end of the penis, which is usually curved. A short epi- 

 phallus, lined by longitudinal rows of small papillae, is developed in 

 Tritjoncplirns (excepting in T. lucanus), but it is not clearly marked 

 off from the narrower vas deferens. The posterior part of the vas 

 deferens next to the penis is slightly convoluted in Triyoiieplirus, 

 and more strongly so in Dorcasia cdexanclri var. rotundata. In 

 Dorcasia the vas deferens is usually only loosely united to the side 

 of the penis, being nearly detached in D. alexundri, and in Trigo- 

 nephrus lucanus it is quite free ; but in the more globular species 

 of Trigonephrus the vas deferens and epiphallus are very closely 

 attached to the wall of the penis, the vas deferens being practically 

 embedded in it towards the genital atrium in some forms, such 

 as T. namaqucnsis. Followed backwards, the vas deferens bends 

 under the female duct and curves up the right side of the swollen 

 free oviduct in most of the species of Trigonephrus ; and in these 

 forms the receptacular duct arises on the left side. But in Dorcaxm 

 and in Trigonephrus lucanus, the vas deferens keeps to the left of 

 the female duct, and the receptacular duct arises on the right side, 

 and crosses over the junction of the free oviduct and the common 

 duct. 



Much connective tissue unites the vagina, free oviduct, and 

 common duct to the adjacent body- wall ; and at the junction of the 

 two latter ducts this tissue is so abundant that it seems to form a 

 partial septum across the body- cavity. 



Spermatozoa (PI. V., figs. 9-11). Head varying in length from 

 005 to -006 mm. ; tapering in front, and curving alternately to the 

 right and left ; broader behind, especially in Trigonephrus. Tail 

 extremely long ; proximal portion, or middle-piece, surrounded by 

 very delicate spiral filaments or flanges, of which there usually 

 appear to be three. An irregular, oval, flexible spermatophore is 

 formed. 



Eggs. According to Binney, Gibbons stated that the eggs of 

 Trigonephrus globidus were of a very large size." It is probable, 

 however, that in this sub-family they do not attain such large 

 dimensions as in some genera of the Acavidae ; for although the 

 embryonic shell is not clearly differentiated from the succeeding 

 whorls, it evidently does not reach the enormous size found in some 

 members of the family. 



* Ann. N.Y. Acad. Sci., 1880, i. p. 361. 



