193 



S. effusus bears some resemblance (o S. vespertinus, Linn. S. strigilatus 

 appears to be similar to the recent shell of the same name. S. appe?i- 

 diculatus is a small smooth elliptical shell, the recent analogue of which 

 is unknown. It derives its name from a little process which projects 

 near the beaks. 



Fragments of shells of this genus are found in the Essex cliff. From a 

 considerable number of these I have been able to make out only two 

 species resembling S. siliqua, Linn, and S. e?isis. It is remarkable, that 

 in the fossil shell agreeing in the characters of its hinge with S. siliqua, a 

 proportionate shortness in its transversal length is observed with that of 

 the fossil S. vagina, described by Lamarck. In one valve of this species, 

 which I am able to say must have measured nearly an inch in its length, 

 from its inferior to its superior edge, the breadth from the anterior to the 

 posterior termination is only two inches and three quarters. The fossil 

 resembling S. ensjs, appears to vary from it only in not being quite so 

 much bowed as the recent shell. 



CXXIII. Sangumolaria. A transverse bivalve, arched on its superior 

 edge, and gaping a little at its extremities. Two hinge-teeth, approxi- 

 mate and articulating, on each valve. 



This genus is exemplified in Sanguinolaria rosea, Solen sanguinolentum, 

 Linn. List. t. 397, Fig. 236. The shells of this genus are distinguish- 

 able from those of Solen, only by their having two teeth in each valve. 

 I am not aware of their having been found fossil. 



CXXIV. Glycemeris. A transverse shell, gaping at both extremities : 

 hinge callous, without tooth. This genus is exemplified in G. incrassata, 

 Lam. Mya siliqua, Chemn. ; but Iain not acquainted with any species 

 of it as a fossil. 



CXXV. Mya. A transverse bivalve, gaping at both ends; ligament 

 internal. The left valve with a hinge-tooth, compressed, rounded, per- 

 pendicular to the valve, and giving attachment to the ligaments. 



Lamarck has not met with any shell of this genus, in a fossil state, in 



the environs of France. 



VOL. in. c c 



