OrERCULATINyE. 4 1 



Sub-fam. OPERCULATINiE. 



Mantle lining the shell. 



Shell external, limpet-like, calcareous or horny. 



Genus OPEltCULATUM, Linnaeus. 



Tentacles dorsal, ear-like, with plicate cavities at their 

 bases ; mouth proboscidiform, retractile, covered by a small 

 oral veil with moderate labial appendages, and concealed in 

 the notch at the fore part of the foot. Foot large and 

 thick, deeply fissured in front, the sides tubercular. 



Shell external, calcareous, orbicular, flattened, with a 

 slightly-raised, conical, sub-central apex ; margin acute, 

 simple. 



8yn. Umbrella, Lam. Acardo, Lam. Umbraculum, 

 Schum. Gastroplax, Blainv. Ombrella, Blainv. Urn- 

 bella, Chem. 



Ex. 0. Mediterraneum, Lamarck, pi. 61, fig. 3. Shell, 

 0. lseve, Linn aus, fig. 3, a. 



The great peculiarity in this genus is the fact of the head 

 being sunk into a deep fissure or cavity in the front part of 

 the foot. The vent is tubular and posterior, and the 

 organs of reproduction are anterior to the tentacles. 



Species of Operculatum. 



Chinense, Chem. Mediterraneum, Lam. 



laeve, Linn. pietum, A. Adams. 



Lamarckianuni, Reclnz. 



