86 



CONCHOLOGY. 



exhibiting the commencement of the inferior tentacula, the upper 

 ones, tubular and cloven ; gills at the edge of the dorsal plait, 

 mouth provided with a short retractile proboscis. 



Shell. Depressed oval oblong, concentrically wrinkled, almost 

 entirely open, rounded and convoluted ; the vertex with a single 

 turn. Inhabits the coast of Devonshire in England. Two 

 species. 



Pleurobranchus Peronii. Pleurobranchus Laqueare. 



FAMILY III. 



Calyptracea. Seven genera. 



1. Genus Parmophomis. PI. IX. 

 .hiimal. Body creeping, thick, oblong ovate, broad behind, 

 obtuse at the extremities ; border of the mantle cleft before, and 

 suspended vertically around ; head distinct, and slit below ; two 

 conical contracted tentacula, at the base of which are placed the 

 eyes, which are somewhat pedunculated ; mouth below, funnel 

 shaped, oblique, truncated and concealed ; branchial cavity open- 

 ing anteriorly behind the head by a transverse fissure. 



Shell. Oblong, very depressed, slightly convex above, obtuse 

 at extremities, anteriorly channeled by a slight sinus, and having 

 towards the posterior part a small pointed apex, inclined back- 

 wards ; the lower surface slightly concave. Inhabits the Austrar 

 lian seas. Four species. 



Parmophorus Australis. Parmophorus granulata. 



P. brevicula. P. ambigua. 



One fossil species. 



2. Genus Emargi7iula. PI. IX. 



Animal. Body creeping, with two conical tentacular, eyes at 

 the external vase ; mantle large, partly covering the margin of the 

 shell ; foot very large and thick. 



Shell. Shield-like, conical ; summit inclined ; the cavity simple, 

 having a notch or hollow cut on its posterior margin ; shells of 



