SOLENACI \. MOLLUSCA. SOLECURTUS. 33 



differs from Deshayes' description of the animal of SOLECU'RTUS 

 stri<rillatus, in some obvious particulars. He makes no mention 

 of the fringe of fleshy teeth along the margin of the mantle, which 

 are so remarkable, and which are probably retractile. The bran- 

 chiae do not enter the siphon ; the foot is not tongue-shaped, but 

 somewhat club-shaped, and bent at a right angle within the shell ; 

 and the siphons are united entirely to their extremities, though 

 the branchial is slightly more elongated than the anal siphon. 



This genus embraces, besides the two species here described, 

 the Sohn radidtus y LIN., (Solecurtus lucidus, Conrad,) SOLEN 

 marimus, WOOD, (Solecurtus Nuttallii,Comad,) SOLEN inflexus, 

 WOOD, and S. pellucidus of Europe. These accord with our 

 shells in all respects, except that the third tooth of the left valve 

 in some of them, is replaced by a marginal elevation simply. 

 They differ in their ovate and compressed form from SOLE- 

 CU'RTUS, and especially do they differ from sub-genus CUL- 

 TE'LLUS by having the beaks placed anteriorly. The sinus of the 

 palleal impression usually extends about half way to the hinge. 



MACH^E'RA NI'TIDA. 



Shell slightly recurved, thick, white, undulated by the lines of 

 growth, covered with a strong, greenish-yellow, shining epidermis, 

 corrugated at the posterior extremity. 



FIGURES 25, 26. 

 State Coll., No. 240. Soc. Cab., No. 1717. 



Shell thick, white, oblong-ovate, beaks small, situated at the 

 anterior fifth of the shell, narrowed behind, rounded at both ex- 

 tremities ; the posterior hinge margin is straight and somewhat 

 compressed, and the basal margin being at the same time regularly 

 curved gives the shell a somewhat recurved aspect. Epidermis 

 thick, shining, as if varnished, of a dusky greenish-yellow or dark- 

 gamboge color, wrinkled obliquely at the posterior extremity, and 

 projecting beyond and folding around the edge of the shell. 

 Lines of growth broadly and prominently rounded, giving a wavy 

 appearance. Within white and strengthened by a prominent rib, 

 which, extending from the beaks, inclining very slightly backwards, 

 and expanding, loses itself in the shell about half way across the 

 5 



