The Non-Marine Mollusca of Portuguese East Africa. 203 



Tropidophora (Ligatella) calcarea (Sow.), 1847. 



1847. Cyclostow.a calcareum Sow., Thesaurus Conch, i, p. 118, pi. 26, 

 fig. 113. D.F. 



Hab. Mozambique (Gibbous). 



L. Marques. Tette (Kirk ; Thomson). 



A well-known species, easily recognisable on account of its strong spiral 

 costulation. 



Tropidophora insularis (?) (Pfr.), 1852. 



(Plate VI, figs. 5-9.) 



1854. Cyclostoma insulare Pfr., Conch. Cab., p. 351, pi. 45, figs. 

 5, 6. D.F. 



Hah. L. Marques. District north of Macequece (Cressy). 



I am unable to find any constant points of distinction between the shells 

 of a large series collected by Cressy and what is generally accepted as the 

 typical form of insularis from Natal, but it will be seen that the anatomy 

 differs to a certain extent. Fuller knowledge of the genus is necessary 

 before we can determine whether the Macequece race is varietally or specifi- 

 cally distinct. 



The following are some notes on the anatomy of this form : — 



External features of the animal (PI. VI, figs. 8, 9). — The tentacles are 

 deep yellow, and are very slightly swollen towards their extremities. The 

 coDspicuoTis black eyes are situated on slight prominences at the outer bases 

 of the tentacles. The rest of the animal is of a drab colour, being darkest 

 on the top of the muzzle. This organ is rather long, and is crossed by 

 transverse grooves, except in the centre of its lower surface, where a pair 

 of longitudinal grooves occurs. The sides of the animal are covered by a 

 very fine network of grooves. The foot-sole is cleft longitudinally, and, 

 as the animal moves, the two halves of the foot are used alternately, the 

 end of the muzzle being also applied to the ground at frequent intervals. 



Pallial organs, etc. (PI. VI, fig. 7). — The blood-vessels, which branch over 

 the greater part of the roof of the mantle-cavity, are edged with black 

 pigment, and therefore stand out very prominently, as shown in the figure. 

 Towards the front end, however, they break up into a fine network of veins, 

 and the pigment becomes diffused over the intervening spaces. An osphra- 

 dium is present at the left side of the mantle-cavity. The kidney is light 

 brown and rounded in outline, although its left side is slightly indented by 

 the pericardium. Posterior to the kidney there is a branched concretionary 

 gland, which was full of opaque white concretions in two of the three 

 specimens examined. 



Central nervous system. — The arrangement of the nerve-ganglia in this 



