LAMELLIBRANCHIATA. 469 



ciculate on the anterior and posterior extremities. The strise recurve over 

 the umbonal ridge, at a slightly acute angle. 



The specimens are casts of the interior in sandstone, and the surface 

 markings are not well preserved. Anterior muscular impression large, not 

 deep, situated just within the margin below the lunule. 



A specimen has a length of 82 mm. and a height of 30 mm. 



This species resembles C. recurva, but diflfers in the strong angular umbonal 

 ridge, which extends to the post-inferior extremity, and by the sharp recurv- 

 ing of the striaB over this ridge. 



Formation and localities. In the Chemung group at Chemung Narrows, and 

 between Elmira and Waverly, Tioga county, N. Y. 



PHOLADELLA, Hall. 1870. 

 Pholadella kadiata. 



PLATE LXXVIII, FIGS. 15-21 ; ani> PLATE XCVI, FIG. 1. 



NuculUes radiata, Conrad. Jour. Acad. Nat. Sci., Phila., vol. viii, p. 248, pL 12, fig. 16. 1842. 

 Pholadella radiata (Conrad), Hall. Prelim. Notice Lamellibranchiata, 2, p. 63. 1870. 



" " " ." Pal. N. Y., vol. V, pt. 1. Plates and Explanations: PI. 78, figs. 



15-20. 1883. 



" truntxUa^ Hall. Prelim. Notice Lamellibranchiata, 2, p. 64. 1870. 



*' oniata, " Prelim. Notice Lamellibranchiata, 2, p. 64. 1870. 



Shell from small to medium size, elongate-ovate, cuneate ; length about twice 

 the height. Basal margin regularly rounded, curving in a greater or less 

 degree according to the age of the individual. Posterior extremity more or 

 less obliquely, or sometimes vertically, truncate. Cardinal line straight, 

 sometimes a little concave. Anterior end short, obliquely truncated by the 

 lunule and narrowly rounded below. Escutcheon large and well-defined. 

 Lunule deep, marked by an abrupt incurving of the margin. 



Valves, in their usual condition ot preservation, moderately convex below 

 and gibbous in the middle. In a well-preserved specimen the valves are 

 very gibbous, the depth of both valves being equal to the height of the shell. 



Beaks sub-anterior, prominent, strongly incurved. Cincture extending 

 60 



