ARCA ZERRA. 



SPECIFIC CHARACTER. 



Margins angulated; valves marked with simple uniform 

 and reiTular grooves radiatinij from the iimbones: shell 

 transversely and obliquely striped with brown. 



SYNONYM. 



Arca zebra, Swainson. Zool. Illiis., No. 26, pi. 118. 



OBSERVATIONS. 



« 



Inhabits the coast of the peninsula of Florida. 



Mr. Swainson has separated this species from the 

 A)Ta Nox of authors, and refers it to his subgenus Bys- 

 soARCA. He observes: "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 adiicre, when young, by the byssiform ej)idermis 

 which covers the exterior. A specimen now before us, 

 which we procured in the bay of Naples, exemplifies this 

 singular property. The present species is not uncom- 

 mon in the West Indies, and has been sent to us from 

 Jamaica. Like all others of this particular type, it is 

 almost constantly covered with coralline substances." 



REFERENCE TO THE PLATE. 



Interior, exterior and dorsal views. 

 PI. 66. 



