BIVALVES. ANOMIA. 59 



the valves Jlattish, the other gibbous at the base^ with a 

 jjj'ochiced beaky generally curved over the hinge: one of 

 the valves often perforated near the base : hinge with a 

 linear^ prominent cicatrix^ and a lateral tooth placed 

 within, but in the fat valve, on the very margin : two 

 bony rays for the base of the animal. 



Of this curious genus of Bivalves, fifty-one species are 

 described; but several out of that number have hitherto 

 only been found in a fossil state. 



The shells are usually inequivalve, one of them often 

 flattish, the other gibbous at tbe bascj terminating in a 

 produced beak, which curves upwards over the hinge. 

 There is frequently a small perforation near the base; 

 through which the animal thrusts a strong ligament, 

 whereby it affixes itself to different marine substances, as 

 fuci, crabs, spines of echini, and especially to the stars of 

 the Madrepora Prolifera. 



The Anomiee differ materially in form, some resem- 

 bling the shape of an oyster, as the A. cepa, A. ephip- 

 pium, &c., all of which have the lower valve fiat and 

 perforated. Others, again, are imperforated and nearly 

 orbicular, as the A. craniolaris, A. placenta, &c., and 

 some are oblong, as the A. pectinata, &c. Many of them, 

 when seen in profile, resemble the form of an antique 

 lamp, as the A. caput-serpentis, &c. and a few are very 

 similar to the hooked or curved beak of a parrot, as the 

 A. psittacea, &c. 



The hinge of the Anomia admits of considerable vari- 

 ation; but its most leading character is that of being fur- 

 nished with a linear prominent cicatrix, and a lateral 

 tooth placed within. On the margin of the flattest valve 

 in many species are placed two bony rays, or linear cal- 



