MOLLUSCA OF British Guiana. 45 



with a large elongated body-whorl and a minute spire. 

 With these also a small pale and rather thick shell, in 

 size and shape very much like Bulimus f rater cuius, will 

 occasionally be noticed. This shell is Leptinaria lamel- 

 lata, and may be recognised by the raised or expanded 

 inner or columella lip. 



The two species o, slugs are commonly distributed 

 and are rather plentiful. They may easily be obtained 

 along the upper part of the central avenue of the Botanic 

 Gardens, in the early morning — the larger of the two 

 species being sometimes found feeding on the fallen 

 flowers of the Oronoque trees (Erythrina glauca) . In the 

 one (Vaginula occidentalis), the body reaches a length of 

 from two to three inches and is covered throughout 

 by a brownish green, or dark and nearly black, coriaceous 

 mantle, entirely destitute of a shell ; in the other 

 (Parmacella sp.) which is much smaller, a shield- 

 like external shell is placed over the raised hump- 

 like middle of the body. The shell is thin, oblong 

 and slightly concave below and destitute of any spire, 

 the edges of the shell being more or less covered by the 

 mantle ; the walking disk or foot is large and pointed 

 behind ; the generative pore is situated on the right, 

 below the large oculiferous tentacle ; and the anal is 

 posterior to the respiratory pore, both being situated 

 toward the middle of the edge of the mantle on the right 

 side. The body is hyaline, but marked along the back 

 with two wide and dark longitudinal bands, and with a 

 variable number of longitudinally placed lateral spots. 



The Bivalves in the list are all species of the river- 

 mussels ; and have been found along the higher Essequibo 

 in the sand pools among the rocks of the rapids, and in the 



