BYSSOARCA Zebra. 

 Zebra Ark-shell. 



Genus. Area. Lin. Lam. Sub-genus. Bvssoarca. Nob. 



Sub-Generic Character. 



Animal fixed by byssiform filaments to other bodies. Shell trans- 

 verse ; umbones remote ; valves gaping in the middle of the 

 ventral margin. 



Specific Character. 



Margins angulated ; valves marked with simple uniform and 

 regular grooves, radiating from the umbones : shell trans. 

 versely and obliquely striped with brown. 



It is somewhat surprising that the sedentary type of the 

 genus Area should have been so long uncharacterized in 

 our Conchologieal Systems ; seeing that the other four 

 types, viz. Area, Pectunculus, Cwculloea, and Nucula, 

 were defined many years ago by the celebrated Lamarck. 

 We have consequently supplied this omission ; and at the 

 same time have selected a species hitherto, we believe, 

 confounded with the B. Noie ; from which it differs in 

 sculpture, colour, and in the umbones being less remote 

 from each other. 



The Animals of these shells affix themselves to other 

 bodies by a particular muscle, which is protruded through 

 the gaping part of the valves ; they also adhere, when 

 young, by the byssiform epidermes which covers the 

 exterior : a specimen now before us, which we procured 

 in the Bay of Naples, perfectly exemplifies this singular 

 property. The present species is not uncommon in the 

 West Indies, and has been sent to us from Jamaica. 

 Like all others of this particular type it is almost constantly 

 covered by coralline substances. 



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