170 Annals of the South African Museum. 



Animal of full-grown specimens from the same locality. — 



Colour drab, possibly due to immersion in strong spirit ; roof of 

 mantle-cavity apparently unpigmented. Left body-lobe divided into 

 two separate portions, the left being rather small and not connected 

 with the right by any fold or ridge (see PI. IV., fig. 6, which also 

 shows the arrangement of the pulmonary veins and the form of the 

 kidney). Pedal gland embedded in the muscles of the foot at its 

 bind end, but emerging into the body-cavity further forward. 



Jaw 1"9 mm. long, rather thin, golden-brown ; broader towards 

 the middle, more pointed at the ends, and rather more curved than 

 in D. coagulum and D. rogersi (PL IV., fig. 24). Eadula of a 

 specimen, the shell of which measured about 21^ mm. in diameter, 

 5xl'8mm. ; transverse row^s of teeth almost straight; teeth less 

 diverse in shape than in D. coagulum and D. rogersi; outer 

 marginals with squarer bases (PI. IV., fig. 16) ; ectocones are present 

 on about five-eighths of the teeth ; formula (39 + 1 + 40) x 139. In 

 another specimen several of the rows of teeth are abnormally 

 shortened and crowded, the formula being (41 + 1 -f 41) x 166, and 

 the radula measures 5-2 x I'S mm. Crop and salivary glands 

 apparently unpigmented. Buccal retractor united with the left 

 tentacular retractor for a longer distance than in the other species. 



Reproductive system (PI. V., fig. 8) : hermaphrodite duct very 

 slender and closely convoluted ; vesicula seminalis long ; common 

 duct abruptly curved at its anterior end ; free oviduct scarcely 

 swollen, receptaculum seminis larger than in D. coagulum and 

 D. rogersi ; vagina long ; vas deferens very loosely attached to the 

 side of the penis ; the part next to the posterior half of the penis is 

 closely convoluted, the convolutions being bound together by a 

 sheath of connective tissue ; penis long, curved and contorted, 

 especially towards the posterior end, though the bends occupy 

 different positions in different individuals. 



Hab. Damaraland. Eehoboth District. 



Type of rotundata in Zurich Museum ; siegmanni in coll. 

 Natermann. 



The pubhshed figures of rotundata hardly convey a proper idea of 

 the actual shell, as they entirely fail to show the well-marked basal 

 sculpture, which is its most prominent characteristic. This 

 unfortunate omission was the cause of its being re-described by 

 Honigmann under the varietal name of siegmanni. However, at 

 the instance of Herr Carl Natermann, cotypes of the last-named 

 form have been compared by Dr. 0. StoU, of Zurich, with the 

 type set of rotundata, and pronounced inseparable. Both were 



