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, spmes 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 withm. On the margin of the flattest valve 
in many species, are placed two cartilagmous 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. electrica, &c. The A. cepa, 
and the A. sella, have a bronze-like appearance; and 
the A. capensis and A. sangumea 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 Anomiz are almost smooth; others, on 
the contrary, are marked with ribs and strize, 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 ina young state, 
becomes so transparent by the process of polishing, 
