Manchester Memoirs, Vol. xlii.{\%(^%\ No, 4i. 29 



latter it is inclined to one side. In this new form, the 

 median sulcus is hardly perceptible. As in L. elliptica, 

 the longitudinal riblets are evanescent at the sides, being 

 about twenty-six in number ; these riblets are more pro- 

 nounced than in that species. Several examples. 



(XcTTTojcapuov, a light nut, the fruit of the hickory, from 

 the shape of the shell.) 



YOLDIA CLARA, Sp. nov. 

 (PI. 2, f 7.) 



Y. testa crystallina^ pellucide tenui, cequivalvi, incBqui- 

 lateraii, umbonibus parvis, approximatis, margine dorsali 

 utrimque leniter declivi, antice oblongo-ovato, margine 

 ventrali convexiusculo, postice paullum producto, dentibus 

 pectinatis, in utraquevalva postice quatiwrdeciin, antice eodem 

 numero, superficie nitidissima^vitrea^concentrice obliquilirata, 

 liris indistinctis. 



Alt. 8, lat. 15, diam. 450 mm. 



Hab. Bushire, Persia, 4 fathoms, mud. 



A very delicate crystalline pellucid Yoldia, the super- 

 ficies concentrically obliquely lirate, and slightly prismatic, 

 the shell is posteriorly produced, anteriorly ovate-oblong, 

 the ventral margin somewhat convex, the umbones small, 

 approximate, dorsally declining on each side ; teeth, 

 pectinate, about fourteen in either valve on each side of 

 the umbones. 



The only species nearly allied to this is F. serotina 

 Hinds, which is also in the Townsendian collection, having 

 been found among shell-growth on the Telegraph Cable at 

 55 fathoms mud, in lat. 25^58' N. and long. 57^3' E. This 

 is not so transparent a shell, and posteriorly not quite so 

 produced, the concentric lirae in Y. serotina are clearer 

 cut, and the umbones more prominent, causing the dorsal 

 margin anteriorly to be slightly arcuate. 



(clarus, clear, transparent.) 



