i372 CAruLiD^]. 



Species of Capidus. 



railitaris, Linn. radiatus, Bars. 



paleaceus, Mke. sagittiferus, Gould. 



pilosus, Desk. Uiigaricus, Linn. 



Sub-gen. thyca, H. and A. Adams. 



Shell crystalline, acutely conical, slightly curved, longitudi- 

 nally grooved ; parasitic on star-fishes. 



astericola, Adams and Reeve. crystallinus, Gould. 



Genus AMATHINA, Gray. 



Head elongated ; eyes sessile on the posterior lateral 

 margins behind the tentacles ; tentacles short, obtuse ; 

 mantle-margin entire, a tentacular median filament at the 

 hind part. 



Shell somewhat depressed, surface with prominent, di- 

 verging, longitudinal ribs ; apex recurved posteriorly and 

 contorted ; aperture large, expanded, oblong, emarginate 

 anteriorly. 



Erv. A. tricarinata, Chemnilz, pi. 41, fig. 2, 2, a. 

 Shell, A. tricarinata, fig. 2, h. 



Amathina differs from Capidus in having prominent 

 longitudinal ridges in front of the shell, which is never 

 covered with epidermis. The animal, which we have 

 examined from a specimen in spirits, in Mr. Cuming's 

 collection, has a very long head, with the eyes sessile at 

 the sides behind the base of the tentacles, and there is a 

 peculiar tapering filament, situated centrally, at the pos- 

 terior extremity of the mantle. 



