140 Annals of tlic South African Museum. 



Such are the chief characters found in those species of Trigo- 

 mphriis and Dorcasia, of which it has been possible to examine the 

 anatomy. Whether these features are possessed by Tulhaghinia 

 also, it is at present impossible to say, for no specimens of this 

 genus have been available for dissection. 



Distribution. — South-West Africa, chiefly near the coast and in 

 the neighbourhood of rivers, from Algoa Bay and Montagu in the Cape 

 Province to the Northern borders of Damaraland. 



Genus TRIGONEPHEUS, Pilsbry, 1905. 

 Proc. Mai. Soc, vi. p. 286. 



Shell rather large, elongate- to compressed-globose, perforate, 

 fairly solid, almost unicoloured. Whorls 4-5, rapidly increasing, all 

 but the earliest covered with close faint transverse striae following 

 the lines of growth, usually combined with a considerable amount of 

 malleation, and, in some species, inconstant tracts of close, micro- 

 scopic, spiral sculpture. Aperture large ; peristome interrupted, 

 margins externally thickened, sometimes to a considerable extent 

 backward from the lip, and narrowly reflexed. 



Animal differing from Dorcasia, in the following respects. Foot- 

 sole entire, without any longitudinal grooves. Kidney broader at 

 the anterior end than in Dorcasia, with no fold along its right side. 

 Pedal gland more or less embedded in the muscles of the foot. 

 Cerebral ganglia pigmonted. Jaw rather broad, and more than 

 2 mm. long. Radula about twice as long as it is broad ; teeth 

 larger than in Dorcasia ; central and lateral teeth tricuspid; in the 

 marginals the endocone gradually unites with the mesocone, and in 

 the outer teeth the ectocone often disappears, though most of the 

 marginals are bicuspid ; bases of central teeth usually a little shorter 

 than the mesocones. 



Reproductive system : free oviduct greatly swollen ; receptacular 

 duct less than twice the length of the free oviduct ; excepting in 

 T. luca)ius, the receptacular duct does not cross the common duct, 

 and the vas deferens curves round the right side of the free oviduct, 

 is closely bound to the penis, and terminates in a short epiphallus ; 

 penis containing rows of prominent rugae, or short papillae, which 

 fuse with one another to form corrugated longitudinal ridges. 



Distribution.— South-West Afeica, for the most part in sandy 



