MY A. 21 



CHAPTER IV 



Second Division. — Bivalves : 14 genera. 



" I FEAR," said Charles, ^' that this new division 

 •will be rather difficult, for my father tells me that 

 we must pay particular attention to the hinges of 

 bivalve shells." 



" Then apply yourself to the study of hinges, 

 Charles, and your difficulties will chiefly disap- 

 pear," answered Mr. Elliot. 



" The hinge of Mya, the first on the list, is 

 easily known. The generic characters are, shell 

 gaping at one end, hinge mostly with one thick 

 spreading tooth, not inserted into the opposite 

 valve. The Mya race burrow in the sand. Here 

 is Mya arenaria, a large thick shell, frequent 

 on the shores of Kent : the large tooth is suffi- 

 ciently plain in this species. Mya truncata 

 (Plate 4) is as common, and the curious mem- 

 branous case, which you will find attached to one 

 end of the shell, is a guide to the species. Both 

 these species are without colour, and have little to 

 attract in their outward appearance. The genus. 



f7 



