722 PROCEEDINGS OF THE NATIONAL MUSEUM. voi. xxvii. 



LIMIPECTEN TEXANUS, new species. 

 Plate XLV, figs. 1,2,3; Plate XLVI, fig. 4 (?); Plate XLVII, figs. 1,2,3. 



Shell large; length nearly equal to or slightly in excess of the width. 

 The largef>t example observed must have been over 65 mm. long 

 when complete. The hinge line is long, though somewhat shorter 

 than the greatest width. The obliquity is slight but appears to be 

 forward as in Lima. 



The convexity of the left valve is moderate or strong in different 

 individuals. The umbo is large, well defined, and incurved. The 

 wings are broad and the outline- is not strongly withdrawn beneath 

 them. They are of nearly equal size, the anterior one being possibly 

 a trifle larger than the posterior. It is also much more strongly 

 defined, for while the posterior wing is depressed and slightly 

 upturned, and therefore bounded by an ill-detined groove, the descent 

 to the anterior wing is abrupt and angular. This wing is flattened 

 and somewhat oblique. The surface is crossed by rather coarse and 

 radiating ribs, which are more or less regularl}^ unequal in size. 

 Frequently three gradations can be distinguished, every fourth rib 

 being large, those half way between somewhat smaller, while others 

 alternating with these two sj^stems are still smaller. The ribs do not 

 extend onto the wings, though sometimes traces of slender ones 

 appear. The surface is also crossed by delicate concentric lamelliB, 

 rather distant and irregular, which are much stronger and more 

 crowded on and near the wings. They cross the shell in scalloped 

 lines with pointed extensions in the striw between the ribs. 



The right valve is much flatter than the left and its surface orna- 

 mentation, though of the same general character, is so difi^erent that 

 one would hardl}^ think of the two belonging together, if found sepa- 

 rately. The posterior wing is flat, and not marked oft' from the rest 

 of the shell. The anterior wing is, on the other hand, sharply defined, 

 and the outline is strongly retracted Ijcneath so as to make a deep 

 byssal sinus. While the umbo of the left valve is prominent and well 

 defined, the right valve practicall}^ lacks this feature altogether. The 

 surface is marked by somewhat depressed ribs, which are much finer 

 and more numerous than those of the opposite valve. They are, as a 

 rule, obsolete over and near the wings, but a few faint and slender 

 ones can sometimes be seen. The concentric lamellae are in like man- 

 ner finer and fainter than those of the left valve. They are obscure 

 over most of the shell, and onlv distinct upon and near the wings. 



There is a broad and massive hinge plate marked by structural lines 

 parallel to the straight lower border, and just beneath the beaks a large 

 distinct fossetto for the resilium wdiich is very oblique and directed 

 backward. Both valves seem to have this structure of the same 

 character and force. Near the center, under the hinge plate, are 



