138 OSTRE\ EDUT.IS. 



after for the purpose of polishing the softer metals. The black 

 fluid which some of the species of this tribe of animals secrete, 

 when dried, is used as a pigment, and is said to form the basis of 

 China ink. 



Many of the Sepiaceee were formerly used as food ; and Aristotle 

 informs us that they were considered in the best condition for the 

 table when nearly ready for spawning. Among the ancients, Di- 

 phelus, Paulus iEgineta, and Galen, observed that they were 

 esteemed highly nutritious and aphrodisiac ; and /Etius recom- 

 mended them to those who were weak in the palestra. The modern 

 Greeks and Romans arc said to use them still as articles of food, 

 and consider the eggs as a great delicacy. 



Class VI.— CONCHIFERA. 

 (Mollusca Acephah, Cuv.) 



Animals soft, inarticulated, destitute of head or eyes, 

 and always fixed in a bivalve shell ; branchiae exter- 

 nal ; circulation simple ; heart unilocular. 



OSTREA EDULIS. 



The common Oyster. 



Order Testacea, Lin. Monomyaira. Family Ostra- 



cea, Lam. 



Gen. Char. Shell adhering, inequivalvc, irregular ; 

 upper valve advancing as the animal increases in age; 

 hinge toothless ; ligament attached to the internal 

 cavity ; one muscular impression on each valve. 



Spec. Char. Shell suborbicular, rugged, with transverse 

 membranaceous folds ; vpper valve flat. 



