INTRODUCTION. 2 1 



CHAPTER III. 



CLASSIFICATION OF SHELLS. 



LINNAEUS ranks Testacea as the third order in his sixth 

 class of animals called Worms. He has made three prin- 

 cipal or grand divisions, viz. Multivalves, Bivalves, and 

 Univalves. 



I. MULTIVALVES. 



SHELLS WITH MANY VALVES. 



1. CHITON: Valves placed in transverse plaits down the 



back. 



2. LEPAS: Valves unequal; body sessile, or on peduncles. 



3. PHOLAS: Shell hivalve, with accessory valves at the 



hinge. 



II. BIVALVES. 



SHELLS WITH TWO VALVES. 



4. MYA : Hinge with generally a broad thick tooth, not 



let into the opposite valve. 



5. SOLEN: Shell open at each end; hinge with a single 



or double subulate reflected tooth, not let into the 

 opposite valve. 



6. TELLINA : Hinge with the lateral teeth of one valve 



not let into the other. 



