SOLECURTUS. 261 



middle, and even retiise towards the incurved ventral mar- 

 gin. The surface which is devoid of regular sculpture, 

 merely showing a few antiquated lines of growth, which are 

 occasionally almost obsolete, is whitish both externally and 

 internally, and exhibits but little if any lustre. Its dull 

 yellowish-olive, or olivaceous straw-coloured epidermis, (in 

 exotic specimens this is sometimes of a drab or fawn- 

 colour,) is strongly wrinkled at each extremity. The sides 

 are very nearly equal ; the anterior, however, is rather the 

 shorter, and its dorsal margin very slightly sloping, and 

 barely convex ; that of the posterior side declines still less, 

 and is almost rectilinear, but is incurved near the short 

 and prominent ligament. Both extremities are bluntly 

 rounded ; the upper part of the anterior one is the more 

 projecting, the lower portion being obliquely rounded from 

 the greater ascent of the ventral margin on that side of 

 the shell. The lower corner of the hinder termination is 

 well rounded ; there is a trifling angularity at the upper 

 corner, which projects almost as far as the other, owing to 

 the absence of declination in the dorsal edge ; the posterior 

 outline is convex. 



The umbones are dorsally depressed, and the beaks in- 

 curved, and not peculiarly distinct. The umbonal ridge is 

 broad, but not greatly elevated ; a corresponding ridge ap- 

 pears from the intervening concavity, to run from the 

 beaks to the front ventral corner, but this is not preceded 

 by any depression of the surface on the other side. The 

 lateral hiation is remarkably ample, the valves only touch- 

 ing at the beaks and at the opposite incurved portion of the 

 ventral edge. The hinge is furnished with two primary 

 teeth in each valve, of which the hinder of the left valve is 

 very oblique, laminar, and very caducous ; the rest are 

 much elevated, recurved, and extending beyond the mar- 



