^52 ZOOLOGY. 



Anterior of the shell obtuse ; margin crenulated ; hinge 

 with two teeth on the centre, and sometimes one or 

 more marginal remote ones. Plate 4, fig. 10. 



Generally found in the sand on the sea shores ; when left 

 dry by the reflux of the tide. 



10. Venus, Venus-Shell. Inhabitant a Te/%^. 



Lips of the shells incumbent at the front margin ; hifigc of 

 three approximated teeth, the lateral ones diverging. 

 Plate 4, fig. 11. 



This genus is separated into three sections, * Subcordate, 

 ** Orbicular, *** Oval, a little angular on the front 

 margin. 



The whole of this elegant genus are oceanic, being either 

 found in the mud or sand, when the tide has receded, or 

 fished up from very deep water. 



11. Spondylus. Inhabitant a Tethys. 



Shell with unequal valves, one at, the other convex, of a 

 rough, hard, and frequently spinous surface, often 

 eared; hinge with two recurred teeth, haTiog an inter- 

 mediate hollow. Plate 4, fig. 12. 



All this genus are found adhering to rocks at consider- 

 able depths in the ocean, from which they are with difficulty 

 detatched. 



