OXCHIDIUM. SOT 



E\^es at the end of nou-retractile, cylindrical peduncles; 

 tentacles none. Mantle coriaceous, large, shield-like, entirely 

 covering the back ; respiratory orifice posterior, at the right 

 side, under the margin of the mantle. Foot narrow, elongate, 

 simple posteriorly, with a locomotive disk. Vent separate 

 from the respiratory orifice, posterior. Male organ under 

 right eye-peduncle ; female orifice at posterior extremity 

 of body. 



Shell none. 



But few species of tliis iiimily have been discovered. They 

 are found to belong to several genera besides the one represented 

 on our Pacific coast, and ai'e variously distinguished by the 

 characteristics of the mantle, smooth or granular in Oncliidella, 

 with arbuseuliform tufts in Peronia, or with a large central 

 tubercle and radiating stria3 in Buchanania. 



lu their habits they are quite marine. 



OXCniDIUm, Been. 



Body oblong or oval, obtusely rounded behind, truncated 

 before; mantle covering the whole body and reflected under the 

 body, coriaceous, convex, tubercular ; foot broad, simple pos- 

 teriorly ; mouth provided with papilUie ; oral append- 

 ages lobate, simple, undivided ; tentacles none ; eyes Fig. 544. 

 at the end of long, club-shaped contractile peduncles. 

 Respiratory orifice posterior, at the right side. Anal 

 orifice separate, posterior ; male organ under the 

 right tentacle, fema e orifice at the posterior ex- 



Onrhi,1h,m 



tremity of the body. catpuutn. 



Shell none. 

 Jaw none. 

 Lingual raeml)rane — ? 



Oncliidiiini carpenteri, W. G. Binn. — Among the mollnsca 

 from the Straits of De Fuca, Mr. Carpenter has detected five specimens 

 of a shelless moUusk, which evidently belong to the genus Onrhidinm. 

 Being preserved in alcohol, it is difficult to obtain any more satisfactory 

 specific characters than the followin<r : The body is oblong, with its ex- 

 tremities circularly rounded ; the upper surface is regularly arched ; 



