Notes on South African Mollusca. 153 



Orange Rivers : Alt. max. 41-5 ; diam. 39'7 ; apert. 23 - 5 X 204 mm.; 

 ends of peristome 18'3 mm. apart. 



Animal of full-grown specimens from the same locality, the shells 

 of which measured about 45 mm. in altitude. 



Colour (in alcohol) grey, the hind end of the foot, the sole and the 

 mantle-edge being the darkest ; roof of mantle cavity unpigmented. 

 Left body-lobe irregularly swollen, its two divisions united by a fold. 

 Pulmonary veins similar to those of the last species, the first 

 branch of the pericardial vein arising nearer to the main pulmonary 

 vein than in T. globulus (PI. IV., fig. 2). 



Cerebral ganglia covered with grey connective tissue. Jaw 

 3-7 mm. long, thick, dark brown (PI. IV., fig. 19). Radula 

 7-^x4^ mm., transverse rows of teeth almost straight; centrals 

 narrow, with rather inconspicuous side -cusps ; outer marginals 

 unusually broad ; mesocones prominently bifid on a larger number 

 of teeth than in the other species (PI. IV., fig. 11) ; formula of one 

 specimen (61 + 1 + 62) x 124, of another (63 + 1 + 62) x 128. Radula- 

 sac not projecting beyond the hind end of the buccal mass. 



Eeproductive system (PL V., fig. 3) : hermaphrodite duct slender, 

 closely convoluted ; vesicula seminalis rather small, swollen at the 

 end but very narrow proximally ; receptaculum serninis oval ; 

 receptacular duct not swollen ; vagina long and rather narrow ; 

 epiphallus very short ; penis abruptly curved at the hind end ; 

 rugae on the longitudinal folds inside the penis much broader than 

 long (PI. IV., fig. 28). 



Hab. LITTLE NAMALAND. PortNolloth; TKaigas; between the 

 Holgat and Orange Rivers ; Koingnaas. 



GKEAT NAMALAND. Ghous ; Angra Pequena. 



Type in British Museum. 



The shell is separable fiom that of T. rosaceus by its more 

 elongate spire and coarser, rib-like striation on the last whorl. The 

 peristome almost invariably shows the square external thickening, 

 which is an irregular feature in the preceding species. 



Both in the general appearance of the animal, however, and in 

 most of the details of its internal anatomy, T. porphyrostoma closely 

 resembles T. rosaceus, and it is evident that these two forms are very 

 nearly allied ; yet the radula of porphyrostoma differs considerably 

 from that of rosaceus, especially in the form of the central teeth, and 

 slight differences seem to be present in some of the soft parts, such 

 as the vesicula seminalis. Moreover, as the specimens examined of 

 both species were found in the same locality, these differences may 

 be regarded as having a greater systematic importance than if the 



