ERVILIA. 343 



at two-fiftlis the distance from the shorter end, and lean 

 sHghtly backward : there is no lunular depression upon 

 the dorsal area. The inner margin is quite entire ; the 

 hinge-margin is wide and shelving inward near the beaks. 

 The hinge, which is destitute of lateral teeth, consists of a 

 broad and profound central triangular cartilage pit, pre- 

 ceded in the right valve by a strong but narrow triangular 

 highly projecting primary tooth, and succeeded by a still 

 narrower very oblique laminar one, which defines it pos- 

 teriorly and occasionally leans over it ; in the left valve 

 the tooth-receptacle is scarcely divided from the cartilage- 

 pit by a narrow and hardly raised wall, and is bounded 

 in front by a very oblique and but little elevated lamina ; 

 a similar but more indistinct one succeeds the cartilage- 

 pit, but the majority of specimens (being worn) display 

 scarcely any traces of dentition in this valve ; none of the 

 teeth are cloven. The muscular impressions are seated high 

 up, and are profoundly impressed ; the pallial sinus is 

 rather large, and not much attenuated at its extremity. 



The ordinary length of the larger shells is nearly half 

 an inch ; their breadth is rather more than half this mea- 

 surement. 



The animal is unknown. 



Notwithstanding that numerous examples have been 

 procured from Cornwall and the Scilly Isles (the only 

 habitats on the British shores), none but single, and more 

 or less worn, valves have hitherto been detected. As 

 the species is taken alive (and in that state it is very 

 beautiful, the interior being rich violet, the external rays 

 of a deep chocolate, and the intermediate spaces whitish 

 or tinged with violet) in the Red Sea, we might have 

 supposed them the produce of some wrecked vessel, but 

 they have been taken continually in these localities from 



