Notes on South African Mollusca. 161 



Diam. maj. 24 -1 ; mm. 20-8; alt. max. 19'2 ; apert. 13'5 x 

 1O8 mm. ; ends of peristome 7 - 7 mm. apart. 



Animal unknown. 



Hab. " SOUTH AFRICA." 



Type in my collection. 



I have seen three specimens, all nearly alike ; the locality is 

 doubtful, but it seems reasonable to suppose that they represent 

 the form mentioned by Layard on p. 158 as inhabiting the George 

 District. 



If this is truly a variety of ambiguosus, it is indeed a remarkably 

 aberrant one ; but there is nothing in its coloration and sculpture, 

 as well as in the general formation of its base and aperture, which 

 is not consonant with its belonging to a close-coiled, high-spired 

 race of the Mossel Bay form, and therefore, so long as the animal 

 is unknown and the locality doubtful, I prefer to give it varietal rank, 

 which it certainly deserves, rather than specific, to which it may not 

 be entitled. 



GENUS DORCASIA, Gray, 1838. 

 (Alexander's Expedition, ii. p. 268.) 



Shell rather large, depressed or depressed-globose, perforate, 

 usually rather thin and corneous with little or no ornamentation. 

 Whorls 5-6, rather gradually increasing ; sculpture consisting of 

 fairly close, transverse, sometimes costate striae, which are more 

 marked and regular than in Trigonephrus, where they pertain rather 

 to the nature of growth-lines. Aperture rather small ; peristome 

 interrupted or continuous, seldom thickened, but more or less 

 broadly reflexed. Umbilicus sometimes deep and perspective, but 

 more frequently shallow and eccentric. 



Animal differing from Trigonephrus in the following respects. 

 Footsole rather indistinctly tripartite, having two shallow grooves, 

 which diverge from a point about 1-| mm. in front of the hind end, 

 and can be traced forward nearly to the anterior end of the sole. 

 Kidney narrower at the anterior end than in Trigonephrus ; having 

 a slight fold or ledge running along its right side, and overhanging 

 the band of modified epithelium which takes the place of the ureter. 

 Pedal gland tending to emerge into the body-cavity. Cerebral 

 ganglia usually unpigmented. Jaw rather narrow, and less than 

 2 mm. long. Eadula nearly three times as long as it is broad; 

 teeth smaller than in Trigonephrus ; central and lateral teeth 

 unicuspid ; marginals usually bicuspid, rarely tricuspid owing to 



