lutrariinjE. 381 



Sub-fam. LUTRARIINiE. 



Mantle-lobes generally united. 



Shell oblong or elongate, gaping behind ; lateral teeth 

 very small, rudimentary, often obsolete, especially in the 

 adult shell. 



Genus TRESUS, Gray. 



Shell ovate, oblong, ventricose, hinder gape roundish. 

 Hinge with the cardinal teeth small ; lateral teeth very 

 small, close to the cardinal ; ligament external, marginal, 

 separated from the cartilage-pit by a shelly plate. 



Ex. T. maximus, Middendorff, pi. 101, fig. 1, 1, a. 



The only species of Tresus at present known is from 

 California; the shell is thick and rugose, with the posterior 

 gape large and rounded. 



Genus DARINA, Gray. 



Shell oblong, compressed, rounded and slightly gaping 

 at each end ; umbo sub -posterior. Hinge with the carti- 

 lage-pit large ; lateral teeth very small, close to the car- 

 dinal ; ligament external, marginal, separated from the 

 cartilage- pit by a shelly plate. 



Syn. Erycina, sp. King. 



Ex. D. solenoides, King, pi. 101, fig. 2, 2, a. 



Darina solenoides was described by King as a species of 

 Erycina ; the shell is thin and compressed, and is from the 

 Straits of Magellan. 



VOL. II. 3 D 



