Weller — Kinderhook Faunal Studies. 101 



elavated above the hinge-line, incurved; umbonal region 

 gibbous, sloping abruptly to the dorsal and anterior margins, 

 and much more gently to the posterior and ventral margins. 

 Surface marked by about 50 simple radiating costae which are 

 crowded posteriorly and anteriorly, being more widely sepa- 

 rated in the middle of the ventral margin where they are at 

 distances of 1 mm. apart. Besides the radiating costae there 

 are a few concentric wrinkles at irregular intervals, which are 

 strongest posteriorly near the hinge-line. 



Remarks. This species was originally described from 

 Michigan, from specimens very much smaller than the one 

 here illustrated. The type of the species has never been illus- 

 trated, but this specimen from Burlington was studied by 

 Winchell and was identified by him with his Michigan shell. 

 The generic reference is somewhat uncertain because the hinge 

 characters are not known. In its general appearance, how- 

 ever, it resembles the Carboniferous shells usually referred to 

 Cardiopsis. 



SCHIZODUS I0WENSI8 n. Sp. 

 PL IV. f. 13-14. 



Shell subcircular in outline, length, 11 mm. and height, 

 10 mm. Hinge-line short, slightly arcuate ; anterior and ven- 

 tral margins regularly rounded, the posterior margin convex, 

 obliquely truncate ; the posterior basal extremity angular. 

 Beaks moderately elevated above the hinge-line, slightly 

 incurved, situated about one-third the length of the shell from 

 the anteri(U' extremity, connected with the posterior basal 

 extremity by a slightly arcuate, subangular, umbonal ridge. 

 The posterior slope from the umbonal ridge concave; the 

 remainder of the shell convex, the greatest convexity above 

 the middle. Surface of the shell smooth. 



Remarks. In the White collection the two specimens used 

 as the types of this species were attached, with others, to the 

 card labeled Cardiomorpha trigonalis, the specimens on the 

 card being designated as types. Among Winchell' s types of 

 this species, however, there are evidently two distinct species 

 represented, one species from the Chonopectus sandstone and 

 the other from the upper yellow sandstone horizon. The 



