46 PALEONTOLOGY. 



to me. On comparison, however, with good specimens of that shell, from 

 the original locality, it is found to differ in having a narrower area, which, 

 with the beak of its ventral valve, is constantly more arched. Its plications 

 are also larger and proportionally less numerous. There are in the collec- 

 tion large numbers of this shell in a good state of preservation, showing the 

 characters mentioned to be quite constant. 



Locality and position. — Three miles south of Pinon Pass, Pinon Range, 

 Nevada; Devonian, probably of the age of the Upper Helderberg limestones 

 of New York. 



LAMELLIBEANCHIATA. 



ANATINID^. 



Genus EDMONDIA, De Koninck. 

 Edmondia? Pinonensis, Meek. 



Plate 1, figs. 8, 8 a. 



Shell transversely-ovate, wider anteriorly than behind, rather gibbous 

 in adult examples, most convex in the central and anterior central regions ; 

 anterior margin rounded from below the beaks into the base ; posterior end 

 narrow, most projecting near the base, where it seems to be very narrowly 

 rounded in outhne ; dorsal border slightly highest a little behind the beaks, 

 from near which point it slopes off more or less rapidly, with a convex out- 

 line, to the posterior basal extremity ; beaks rather depressed, moderately 

 convex, and placed about one-fourth the entire length of the valves behind 

 the anterior margin ; anterior muscular impressions shallow, elongate-sub- 

 ovate, and placed near the margin, with its longer axis ranging nearly 

 vertically ; posterior so faintly marked as not to be apparent on internal 

 casts. Surface of casts smooth, or only showing obscure traces of con- 

 centric marks of growth, with a shallow, narrow furrow, and some appear- 

 ances of an obscure ridge, extending for a short distance obliquely upward 

 and forward from near the posterior basal margin toward the umbones. 

 Hinge unknown. 



Length, 1.33 inches ; height, 0.95 inch ; convexity, about 0.60 inch. 



At the same time that this species is here referred provisionally to the 



