38 THE VOYAGE OF H.M.S. CHALLENGER. 



Section K. 



Teeth.-;— A. single acute denticle in the right valve in front of the cartilage-pit, and a 

 long shelf-like process parallel with the posterior dorsal margin in each valve. 

 Cartilage-Pit. — Small, central or oblique. 

 Surface. — Concentrically striate. 



NecBra claviculata, Dall. | Necera injlata, Jeffreys. 



NeoBra congenita, n. sp. 



Section L. 



Teeth. — None in either valve. 



Cartilage. — Small, oblong, attached to a thin shelly process and directed posteriorly. 



Surface. — Concentrically lamellar or striated. 



Necera angularis, Jeffreys. | Necsra sulcifera, Jeffreys. 



Section M. 



Teeth. — None in either valve. 

 Cartilage. — Short, anteriorly inclined. 

 Surface. — Eadiately costellate. 



Necera fragilissima, n. sp. 



The subjoined Table will show at a glance the considerable difference in the structure 

 of the hinges of the subgenera or sections. In some cases the teeth appear to be 

 the same, as in A and B, and L and M, but in these instances there are other 

 differences in the cartilage or sculpture which constitute the chief points of distinction. 



