V 



XYLOPHAGA. 



TESTA orljicularis, sequivalvis, iaaequilateralisy 

 anticfe hians, (hiatu postic^ angulato) valvis 

 accessoriis duabus, subtrigonis, fornicatis, 

 dente cardinali minuto et costa, in utraque 

 valva, interna ab umbone ad marginem basalem 

 decurrente; impressionibus muscularibus binis, 

 postica magna, obovata ; antica minore, margim 

 siiperiore imposita. 



Wb are obliged to Dr. Turton for his very liberal com- 

 munication of several specimens of this new and very- 

 interesting Genus, as well as for the discovery and first 

 description of it. A single specimen has also occurred 

 in a piece of stick thrown up at Grav^send, for the use 

 of which we are obliged to Mr. Crouch. 



The two valves approach very much in form to those 

 of Teredo; there are, however, two or three characters 

 by which Xylophaga may be distinguished from that 

 Genus; these are, the want of a shelly tube and of those 

 internal appendages common to Pholas and Teredo, gene- 

 rally called teeth, and the addition of two small accessory 

 valves; it appears also to be destitute of the spatulate 

 opercula found in the Teredinae. 



Shell nearly orbicular, equivalve, valves inequila* 

 teral, gaping in front, the opening having an angular 

 termination at the back. Two small, rather triangular, 

 calyciform accessory valves are placed over the anterior 

 side of the hinge, and there is a small curved tooth lying 

 close to the umbo within in each valve; as well as an 

 internal rib running from the beak to the basal margin 

 with a corresponding depression on the outside. The 

 posterior muscular impression is large and obovate ; the 



