204 KELLIID.E. 



Genus II. MONTACU'TA * Turton. PL V. f. 1. 



Body oval, rather thick : mantle protruded, and fringed with 

 short cirri : excurrent tube sessile : foot large, tongue-shaped. 



Shell triangularly oval or oblong : cartilage proportionally 

 large, placed underneath the beak on the smaller and narrower 

 or posterior side : hinge furnished with two strong lateral teeth 

 in each valve. 



Montagu preeminently deserves to have his name 

 commemorated in the present genus, because all the 

 known British species were discovered and admirably 

 described by him. Two out of the three are dwellers 

 in mud : the other has a singular habitat, being inva- 

 riably found attached to the spines on the under side 

 of Spatangus purpureus and other Echinoderms of the 

 same kind. 



The founder of this genus, Turton, says that the 

 hinge is furnished with cardinal teeth but with no lateral 

 ones. This appears to be a mistake ; at least I con- 

 sider the scheme of dentition to be exactly the reverse 

 of the above. The entire space under the beak in the 

 hinge of each valve is occupied by the cartilage ; and 

 this is the only place where cardinal teeth must be 

 looked for. The teeth in all the British species of Mon- 

 tacuta are long and laminar, one on each side of the 

 cardinal area, and diverging obliquely inwards. A deep 

 cavity or indentation is thus formed in the hinge, resem- 

 bling the letter V reversed, and enclosing the cartilage. 

 The sides of this letter represent the usual shape and 

 position of lateral teeth. Cardinal or hinge teeth lie 

 immediately under the beak, and are either tubercular 

 or short. The cartilage is in some species calcified at 

 its point of attachment, and in consequence of its com- 



* Dedicated to the memory of Colonel Montagu, one of our best zoo- 



