ACEPHALA TESTACEA. 267 



CYC LADES, JBruguieres, 



Separated from Venus by Bruguieres, like the Cardia and Donaces, has two 

 teeth in the middle of the hinge, and before and behind two salient and some- 

 times crenulated plates ; but the shell, as in several species of Venus, is more 

 or less rounded, equilateral, and transversely striated. The animal has 

 moderate tubes. The external tint is usually grey or greenish. The Cyclades 

 inhabit fresh water. 



CORBIS, Cuvier. 



Marine testaceous Acephala, transversely oblong, which have also stout middle 

 teeth, and well marked lateral plates ; their external surface is furnished with 

 transverse ribs, so regularly crossed by rays that it may be compared to wicker- 

 work. In the , 

 TELLINA, Linneeus, 



There are in the middle, one tooth on the left and two teeth on the right, 

 frequently forked, and at some distance before and behind, on the right valve 

 a plate, which does not penetrate into a cavity of the opposite one. There is a 

 slight plica near the posterior extremity of the two valves, which renders them 

 unequal in that part, where they are somewhat open. 



The animal of the Tellinse, PERON^IA, Poli, like that of the Donaces, has 

 two long tubes, which withdraw into the shell, and are concealed in a dupli- 

 cature of the mantle. 



Their shells are generally transversely striated, and decorated with beautiful 

 colours. 



LUCINA, Bruguieres. 



Separated lateral teeth, as in the Cardia, Cyclades, &c., that penetrate 

 between the plates of the other valve ; in the middle are two teeth, frequently, 

 but slightly apparent. The shell is orbicular, and without any impression of 

 the retractor muscle of the tube ; that of the anterior constrictor, however, is 

 very long. 



The living species are much less numerous than those that are fossil ; the 

 latter are very common in the environs of Paris. 



VENUS, LinncEUs. 



This genus comprises many Testacea, whose general character consists in 

 the teeth and plates of the hinge being approximated under the summit, in a 

 single group. They are usually more flattened and elongated, in a direction 

 parallel to the hinge, than the Cardia. The ribs, when there are any, are 

 almost always parallel to the edges, being directly the reverse of their arrange- 

 ment in the Cardia. 



The animal is always furnished with two more or less protractile tubes, 

 sometimes united, and with a compressed foot, which enable it to crawl. 

 This genus is now divided into Petricola, Crassina, Cytherea, Capsa, Corbula, 

 Mactra, &c. The common Clam is a true Venus. 



