214 MR. CONRAD'S NOTES ON SHELLS. 



SANG UINOL ARIA, Lam. 



S. NUTTALLii, Cov. Jour. Acad. Nat. Sc Vol. 7, p. 230, PI. 17, fig. 6. 

 PsAMMOBiA DECORA, Hiuds. Zool. of the Sulphur, PI. 19, fig. 6, 7. 



PHOLADOMYA. 



This shell which Deshaj^es referred to Panopea, has a highly perlaceous substance, 

 and is destitute of cardinal teeth. The nacre, and different form of the muscular 

 impressions, appear to me sufficient to exclude it from Glycimeris, Lam., to which it 

 approaches nearer than to Panopea, Aldrov, 



If this Miocene fossil is inadmissible in the genus Pholadomya, I propose a new 

 generic name, Margarilaria. 



PARAPHOLAS, Con. 



Shell pholas-like ; dorsal margins widely folded over the valves: accessory valves two, nearly similar in 

 form, elongated, one extending from the umbo to the posterior extremity ;. the other united to the base ; 

 hinge plate thick; adductor muscular impressions greatly elongated. 



The peculiar character of the accessory valves which appear as though soldered 

 to the shell; the elongated muscular impressions so different from those in other 

 genera of Pholadida ; the form of the pallial impression, and the valve on the base, 

 prove a very distinct organization in the animal, and marked distinctive generic 

 characters. The accessory valves are only tM'o, with a medial suture, and are much 

 alike in form, the dorsal valve being shortest and truncated at the beak. On the 

 back there is a strong resemblance of four other valves caused by a wide folding over 

 the valves. The pallial impression descends in a nearly direct line from the 

 adductor muscle to an elongated cicatrix, of an oblong square shape, which joins the 

 basal margin. 



P. CALiFORNiCA, Cou. Joum. Acad. Nat. Sc, Vol. 7, p. 236, PI. 18, fig. 35. Revue Zool. par la Soc. 



Cuv. 1839, p. 357. 

 P. JANELLi, Desk. Mag. de Zool. 184-0, PL 14, 15. Chenu. Illus. Conch. PI. 3, fig. 4. 



PECTEN. 



P. FRAGosus. — Ovate ; inferior valve nearly flat ; ribs eight, six of which are very large, rounded, 

 profoundly elevated, nodose, longitudinally sulcated ; intercostal spaces very narrow, crossed by 

 transverse elevated laminae, and destitute of longitudinal lines; posterior ear produced, margin dentate; 

 colour deep orange. Length 2 inches : height the same. 



Inhabits the West Indies. 



Differs from P. nodosus in having fewer, sulcated and much larger ribs, narrower 

 interstices with transverse laminae ; and in the flatness of the inferior valve. The 

 anterior and posterior submargins have longitudinal lines, but the intercostal spaces 

 are without any. 



