66 BIVALVES ANOMIA. 



hinge. There is frequently a small perforation in the 

 beak, near the base, through which a strong ligament is 

 protruded, whereby the animal affixes itself to different 

 marine substances, as fuci, crabs, spines of echini, and 

 especially to the stars of the Madrepora Prolifera. 



The hinge of the Anomia admits of considerable va- 

 riation ; but its most leading character is that of being 

 furnished with a linear prominent cicatrix, and a lateral 

 tooth placed within. On the margin of the flattest valve 

 in many species, are placed two cartilaginous substan- 

 ces, which serve as a base for the animal ; but some 

 have only one of these in each valve. The margin is fre- 

 quently crenated, notched, or toothed, but in many it 

 is perfectly smooth. 



The interior of the shells of this genus has often 

 a silvery appearance ; the prevailing color of the ex- 

 terior is a dirty yellow, or dusky white, and some are 

 bright yellow, as the A. electiica, &c. The A. cepa, 

 and the A. sella, have a bronze-like appearance ; and 

 the A. capensis and A. sanguinea exhibit a beautiful 

 pink or red coloring. The A. psittacea, and other si- 

 milar species, have a dingy or olive black color, and 

 a few are found of a shining, jet black. 



Some of the Anomiae are almost smooth ; others, on 

 the contrary, are marked with ribs and striae, which in 

 the A. muricata are covered with scales, and hollow 

 spines of considerable length. 



The shells are generally thin and delicate, and usually 

 semitransparent. The A. placenta, when in a young state, 

 becomes so transparent by the process of polishing, 



