41 



<genu0 iv. 



MYA:* 



SHELL BIVALVE, OPEN AT ONE END; HINGE WITH 

 ONE OR MORE SOLID, THICK, SOMEWHAT SPOON- 

 SHAPED TEETH, NOT INSERTED INTO THE OPPO- 

 SITE VALVE. 



Subdivisions. 



* Hinge with one or two rounded Teeth, not in- 

 serted into the opposite Valve. 

 ** Hinge callous without Teeth. 

 *** Hinge with Teeth inserted into the opposite 

 Valve. 

 Hinge toothless, with a hollow rounded recep- 

 tacle for the Cartilage. 



-*." *R" Tp -7V 



* Hinge with one or two rounded Teeth, not inserted 

 into the opposite Valve. 



glycymeris. 1. Shell oblong, very thick, trans- 

 versely wrinkled, and gaping at both ends ; 

 hinge with a thick primary tooth. 



* The following is a remark of my friend Dr. Leach's ; an J that the arrange- 

 ment of the natural family to which the Myae belong, requires much revision, 

 is undeniable. " The Linnaean Genus Mya affords an excellent example of 

 the evil resulting from artificial arrangement. Under this head we find several 

 Genera with distinct animals, and shells having no affinity with each other; 

 some not even agreeing with the almost unlimited characters laid down . many 

 inhabiting the sea, others fresh water, confusedly mixed together without even 

 any distribution into intelligible sections." Zoological Magazine, I. p. 119. 



