51 



valve, and a concave tooth and remote lateral one in 



the other : ligament internal. 



K. SUBORBICULARIS. Turt. B. p. 57. t. 1 1./. 5, 6. 

 />. 430 MYA. S. Mont. p. 39. and 564. t. 26. 

 /. 6. im. T. 8.^.41. Wood. G. C.p. 111. 2). p. 

 55. Sub-orbicular, equilateral, very convex, yel- 

 lowish white, with slight concentric striae ; ventral 

 edge nearly straight, ends rounded ; cuticle thin, green- 

 ish, prismatic. . Roots of sea-weed. 



K. RUBRA. Turt. B p. 58. t. 11. /. 7, 8. F . p. 

 430. CARDIUM R. Mont, p. 3. t. 27. f. 4. Wood. 

 G. C.p. 213. D.p. 131. Walk. t. 3./. 86. Oval, 

 inequilateral, reddish and very finely shagreened (often 

 paler or covered with a rough green or brown coat; 

 beaks prominent, subterminal, under which the margin 

 slopes in an incurved manner towards the smaller end : 

 inside glossy purple. 0,80. ..0,10. Roots of sea-weed. 



GENUS. MONTACUTA. TURTON. 

 Oval or oblong, equivalve, inequilateral, mostly closed; 

 hinge with two teeth in each valve and a cavity 

 between them ; lateral teeth none : ligament in- 

 ternal. 



M. SUBSTRIATA. Turt. B. p. 59. t. II. f. 9. 10. 

 P.p. 465.- LIGULA S. Mont. sup. p. 25. MY t 

 c 2. 



