No. 109.] 



141 



STROniOMENA ( SlROrilODONTA) TEXTILIS ( 11. S.). 



Shell very thin, semioval, sometimes longer than wide, much 

 compressed; hinge about equal to the greatest breadth, nearly 

 rectangular at the extremities : dorsal valve scarcely concave : 

 ventral valve Hat, or very slightly convex; area linear, striated 

 vertically, and marked by a narrow linear callosity in place 

 of the foramen. Surface marked by slender distant elevated 

 radiating stria?, which increase by interstitial addition : spaces 

 between the stride marked by extremely line radiating lines, 

 which are crossed by minute closely arranged concentric strise. 



This shell differs from the preceding in its nearly flat ventral valve and 

 less prominent radiating striae, while the concentric stria; are very con- 

 spicuous on the surface between the coarser ones. There are from four to 

 twelve finer radiating striae between the coarser ones, which become less 

 conspicuous towards the beak. 



The alternations of the striae are not unlike those of Strophomena iii- 

 terstilialis ( Phillips), and S.inequistriala (Conrad); but the flattened 



StB.0PH01IENA TEXTILIS. 



