LAMELLIBRANCHIATA. 487 



narrowly rounded and truncate above. Cardinal line slightly arcuate. 

 Anterior end short, declining abruptly from the beak and rounded below. 



Right valve gibbous in the middle and umbonal region. Left valve more 

 depressed. 



Beaks sub-anterior, appressed, rising a little above the hinge-line. Cinc- 

 ture shallow, undefined, continued to the basal margin. Umbonal slope 

 obtuse, prominent, extending to the post-inferior extremity. 



Surface marked by fine concentric striae and on the middle and anterior 

 portion by strong regular concentric undulations, which are sometimes dupli- 

 cate on both .sides of the cincture, mainly on the posterior half of the shell. 

 Entire surface covered by fine radiating striae. 



Hinge-line marked in the posterior part by a slender groove. 



Three specimens measure respectively 8, 15 and 15.5 mm. in length, and 

 4.5, 8 and 8.5 mm. in height. 



This species resembles C. indenta from the Hamilton group, but it is more 

 elongate, comparatively narrower at the posterior end, the umbonal slope in 

 the right valve is more direct than in the right valve of that species. 



Formation and localities. In the Waverly sandstones, Licking and Medina 

 counties, Ohio, and at Warren, Pa. 



Cypricaedinia sulciperus. 



PLATE LXXIX, i^IG. «!. 



Sang abwlitai milcif eras, Wischbll. Proc. Acad. Nat. Sci., Phila., p. 14. 1863. 

 In part Oypricardinia indenta (Conrad), Hall. Pielim. Notice Lamellibraiichiata, 2, p. 83. 1870. 

 " " " •' " " Pal. N. Y., vol. V, pt. 1. Plates and Explanations : 



PI. 70, figs. 6-23. 1883. 



The figure is given from a specimen in the Yellow sandstone, at Burlington, 

 Iowa, and is three times enlarged. The material in our possession is not suffi- 

 cient to determine its intimate relations with the other species. It is, how- 

 ever, marked with fewer undulations than any other form here described. 



