Notes on SoutJi African Mollusca. 355 



Reproductive system (PI. V., fig. 4) : hermaphrodite duct and 

 vesiculaseminalis absent from the mature specimen, having been left 

 in the shell with the posterior division of the liver when the animal 

 was extracted ; receptaculum serninis rather large, tapering pos- 

 teriorly ; receptacular duct scarcely thickened towards the anterior 

 end; vagina short, swollen posteriorly ; epiphallus very short ; penis 

 somewhat curved at the hind end, swollen near the genital opening, 

 the vas deferens being more deeply embedded than usual in the wall 

 of the swollen part ; rugae on the longitudinal folds inside the penis 

 much broader than long, as in the last three species (cf. PI. IV., 

 fig- 28). 



Hal). LITTLE NAMALAND. Quaggafontein ; Ookiep ; Wilde 

 Paards Hoek ; hills west of Groen Kloof (Rogers); Muishond ; 

 Meskiep ; Kamaggas (Schultze). 



Type in British Museum. 



This uncommon but rather widely distributed species is easily 

 recognizable by its thin brown shell and white peristome. 



The colouring of the animal also distinguishes it from all the pre- 

 ceding species. Possibly the concentration of the dark pigment into 

 black patches and spots on the roof of the mantle-cavity is connected 

 with the thinness of the shell, which would allow more light to 

 penetrate to the lung than in the case of forms with thicker shells. In 

 its internal anatomy T. natnaquensis closely resembles T. gypsinus ; 

 but it differs from that species, as well as from the other members 

 of the genus, in the enlarged base of the penis. 



TRIGONEPHRUS NAMAQUENSIS (Melv. & Pons.), var. PROCERUS, nov., 



1915. 



(Plate II, f. 8, 9.) 



1912 Tricjoncphnis gypsinus, M. & P. (pars], Conn., Ann. S.A. 

 Mus. xi. p. 155. 



Shell comparatively small, ovate, perforate, thin, nearly trans- 

 parent, uniform pale corneous except the umbilical region and 

 peristome, which are white ; interior nacreous. Spire produced, 

 about two-thirds the length of the aperture ; apex obtusely rounded. 

 Whorls 4-|-, inflated, rapidly increasing, covered, after the first two, 

 with extremely faint, regular, close, transverse striae, and faint, 

 irregular pitting or malleation, hardly visible without a lens, which 

 imparts to the surface a slight appearance of spiral sculpture. 

 Suture deep, simple. Aperture quadrate-ovate ; peristome slightly 

 rpflexed ; outer lip making with the body-whorl an obtuse angle of 



