INVERTEBRATES. 529 



Genus CONOCAEDIUM, Bronn. 



CoNOCARDrtTM obliquum, M. and W. 



PI. 33, Fig. 4. 

 Conocardium obliquum-. Meek and Worthen, 1865. Proceed. Acad. Nat. Sci., Pliilad., page 249. 



Shell rather small, obliquely subtrigonal, gibbous ; anterior side 

 (posterior of Woodward) very obliquely and abruptly truncated with a 

 forward slope, and flattened so as to present a regular cordate outline 

 in a front view; anterior auricle narrow, but of unknown length ; base 

 very short; posterior margin sloping up from the base so as to intersect 

 the hinge at an angle of about 45°, rather widely gaping, and crenate 

 its entire length. Beaks moderately prominent, small, strongly incurved ; 

 umbonal slopes very prominent, angular, and directed obliquely forward 

 to the angular anterior basal extremity. Surface ornamented with 

 rather sharply elevated, thread-like, subcrenate radiating ribs, narrower 

 than the depressions between; each of these depressions on the poste- 

 rior and flattened anterior sides of the valves occupied by a smaller 

 intermediate rib ; entire surface also marked by fine very regular radi- 

 ating and concentric strise, so as to produce a neat, minutely cancellated 

 sculpturing, as seen under a magnifier. 



Length from the posterior extremity to the produced antero-basal 

 angle, 0.70 inch ; bight from the latter to the beaks, 0.50 inch ; length 

 from the beaks to the posterior extremity, 0.37 inch ; convexity, 0.44 

 inch ; breadth of posterior hiatus, 0.17 inch. 



We know of no other species liable to be confounded with this. Its 

 most marked features are the great backward obliquity of its umbonal 

 axis, by which its beaks are placed even a little behind the middle of 

 the body part of the shell ; and the beautiful regular cancellated style 

 of ornament seen between the ribs, under a magnifier. 



Position and locality : Coal Measures ; Wabash cutoff, Posey county, 

 Indiana. 



Genus PLETJEOPHOEUSI King. 

 Pletxeophoetjs ? angtjlattjs, M. and W. 



PI. 33, Fig. 5. 

 Pleurophorus 1 angulalus, Meek and Worthen, 1865. Proceed. Acad. Nat. Sci., Philad., page 247. 



Shell oblong, about twice and a half as long as high, rather convex; 

 cardinal and ventral margins straight and parallel, or the latter very 

 faintly sinuous along the middle; posterior side (which is a little imper- 

 fect in our specimen,) apparently obliquely truncated above, and very 



