178 Transactions of the Royal Society of South Africa. 



the hinder end of the penis, and has a narrow ridge running along its pos- 

 terior convex surface. This structiire, like the corresponding one in the 

 last species, is very like a short epiphallus ; but it is more probable that in 

 both species it is really a terminal appendix to the penis, and that the vas 

 deferens does not open into it, but runs forwards embedded in its outer 

 wall, forming the ridge mentioned above, and opens independently into the 

 hinder extremity of the penis. It would be well, however, for any one who 

 may have an opportunity of dissecting more full-grown specimens of either 

 of these species to make a fresh examination of these organs by means of 

 serial sections, so as to remove all doubt as to their exact morphology. 



The penis is broad posteriorly, but tapers towards the narrower genital 

 atrium. It is lined by longitudinal rows of small papillae, except on the 

 ventral side towards the posterior end, where there is a thin-walled area 

 without papillae, bounded by two thick folds which converge and meet 

 anteriorly. The penial retractor is inserted at the junction of the vas 

 deferens with the end of the penial appendix ; it arises, as already men- 

 tioned, from the retractor of the right tentacles, and not from the 

 diaphragm. 



The head of the spermatozoon is pointed in front but somewhat swollen 

 posteriorly, and is scarcely -004 mm. in length. The tail is remarkably 

 long, attaining a length of about -37 mm. ; its anterior part has a spiral 

 structure, as shown in PI. VII, fig. 4. 



Affinities. — This species differs considerably from Ps. boivini in its 

 radula (compare PI. VII, fig. 1 with text-fig. 19), as well as in the apical sculp- 

 ture of its shell, and in the character of the columella, which differs less 

 from that found in Pseudoglessula s. s. than does that of Ps. boivini. Never- 

 theless the anatomical as well as the conchological characters of the present 

 form leave little doubt that it is rightly placed in the same section of 

 Pseudoglessula as the last species. It is important to notice that in both 

 these forms the penial retractor arises from the columellar muscle, as in 

 so many of the Achatinidae, and not from the diaphragm, as Pilsbry states 

 that it does in Ps. stuhhnanni (Mts.),* a species which Germain includes 

 in his subgenus Pseudocerastus. 



Pseudoglessula {Pseudocerastus) gibbonsi (Taylor), 1877. 



1877. Buliminus gibbonsi Taylor, Q.J. of C. i, p. 280, pi. 3, fig. 1. D.F. 



1899 „ boivini Morel., var., Smith, P.Z.S., p. 587. N. 



Hab. Mozambique (Gibbons). 



L. Marques. Mtisherra E. Valley (Cressy). 



It is with much diffidence that I assign the series from the Mtisherra 



* Bull. Amer. Mus. Nat. Hist., vol. xl, 1919, p. 154. 



