154 Annals of the South African Museum. 



specimens had been collected in different districts. The anatomical 

 evidence seems, therefore, to support the view that T.porpTiyrostoma 

 and '/'. rosaceus are distinct, though closely related, species. 



TRIGONEPHEUS NAMAQUENSIS (Melv. & Pons.). 

 (PI. II, f. 7. PL IV, f. 3, 8, 12, 20. PI. V, f. 4.) 



1891 Helix (Dorcasia) nai/taqucnsis, M. & P., A.M.N.H. viii. 

 p. 237. D. 



Shell slightly elongate-globose, narrowly perforate, thin, smooth, 

 semitransparent, uniform yellow-brown, interior nacreous, peristome 

 white and glossy. Spire moderately produced, about three-fifths the 

 length of the aperture ; apex very blunt. Whorls 4^, rounded, rapidly 

 increasing, all but the apical covered with very faint, close, regular, 

 straight, transverse striae, and rather faint, irregular malleation, 

 with occasional traces of close, microscopic, spiral sculpture. Suture 

 simple, well denned. Aperture ovate ; peristome narrowly retiexed, 

 outer lip making with body-whorl an angle of about 130 ; callus 

 faint. Columella erect, slightly concave, margin rather broadly 

 reflexed, almost concealing the narrow perforation. 



Dimensions of a specimen from " South Africa" : Alt. max. 26'3; 

 diam. 24 - 9 ; apert. 16'1 X 13'4 mm.; ends of peristome 11'7 mm. 

 apart. 



Animal of the above and another specimen from the same locality,, 

 one incomplete and the other immature. 



Colour (in alcohol) : foot and mantle-edge pale yellowish buff ; 

 head tinged with grey on the top ; roof of mantle-cavity conspicuously 

 mottled with black, the mottling extending back over the pericardium, 

 but being most concentrated just behind the mantle-edge and near 

 the rectum ; numerous irregular black patches occur on the outer 

 surface of the roof of the cavity, while minute black specks are 

 sparsely scattered over its inner surface. Left body-lobe divided 

 into two portions connected by a very slight fold or ridge ; left 

 division much smaller than the right. Pulmonary veins : two chief 

 efferent vessels bifurcating not very far from their origin (PI. IV. v 

 fig. 3). 



Cerebral ganglia covered with dark grey connective tissue. Jaw of 

 the full-grown specimen 2'75 mm. long, thin, yellow-brown (PI. IV., 

 fig. 20). EadulaS x 3 mm., transverse rows of teeth nearly straight ; 

 centrals with rather narrow median cusps (PI. IV., fig. 12) ; formula. 

 (53 + 1 + 55) x 114. Radula-sac not projecting beyond the hind 

 end of the buccal mass in the full-grown specimen. 



