190 SILURIAN MOLLUSCA. 



Anodontopsis quadratus (M^Coy). 



Sp. Char. Rotundato- quadrate, slightly oblique, with about three- 

 fourths of the length compressed, slightly and evenly convex, 

 the posterior ridge obtuse, and posterior slope obscurely 

 marked ; beaks very small, subcentral ; anterior and posterior 

 sides of nearly equal width, the former broadly rounded, the 

 latter with an obscure, slightly oblique truncation; dorsal 

 margin slightly arched, ventral margin nearly straight, slightly 

 convex. Width 9|^ lines, length 1 inch. 



The peculiar figure produced by the shortness of the posterior 

 side and less convexity easily distinguish this from the A. lavis 

 (Sow. sp.) Casts show the anterior ovate adductor, a faint cla- 

 vicular ridge extending from in front of the beak to its upper 

 posterior edge ; a short cardinal tooth under the beak, and the 

 slender anterior and posterior lateral teeth close under the mar- 

 gin, the latter extending almost to the end of the hinge-line. 



Common in the tilestone of Storm Hill, Llandeilo. 



(Col. University of Cambridge.) 



Anodontopsis securiformis (M^Coy). 



Sp. Char. Sub rhomboid al, compressed, sides evenly convex ; 

 diagonal ridge angular, sharply defined towards the beak; 

 slightly concave towards the posterior slope, which is flattened 

 and steep ; beaks small, prominent, about one-fourth of the 

 length from the anterior end, which is semicircularly rounded ; 

 ventral margin regularly convex ; posterior end narrowed, ob- 

 liquely truncated, with a straight edge ; hinge-line straight, 

 as long as the truncated posterior edge, internal posterior car- 

 dinal ridge very delicate, close under the hinge-line ; anterior 

 adductor small, oval, with a short slender ridge from the beak 

 to its posterior edge. Length 10 lines, proportional width -^-^-j^, 

 length of anterior end 3%^^, length of anal edge ■^■^q, depth of 

 one valve -^-^q. 



There is some slight variation in the proportional width of this 

 species, the shortest varieties of which are however much larger 

 and with a more acutely truncated posterior end than the Cypri- 

 cardia deltoidea or Isocardia axiniformis (Phill.) of the carboni- 

 ferous and (?) Upper Devonian (of S. Petherwin) rocks, to which 

 the species is -most allied. 



Common in the green micaceous quartzite (Upper Ludlow) of 

 Benson Knot, Kendal, Westmoreland. 



{CoL University of Cambridge.) 



CUdophorus ovalis (M'Coy). 

 Sp. Char. Oval, width two-thirds the length ; anterior and pos- 





