FOSSILS OF THE WAVEBLT GKOUP. 255 



erly?), at Dry Canon, Oquirrli Mountains, Logan and Ogden Canons, 

 Wahsatch Eange, Utah, collected by S. F. Emmons, esq. We have also 

 seen several specimens of it in collections from a white limestone brought 

 from the Black Hills by Mr. G. Bird Grinnell, in 1874. 



Spieifera Alba-pinensis n. sp. 



Plate IV, figs. 7-8. 

 Compare Spiri/era biplicatus Hall, Geol. Eept. Iowa, vol. 1, pt. ii, pi. 7, fig. 5, p. 519. 



Shell rather below a medium size, transversely elongate, greatly 

 extended on the hinge-line, with submucronate extremities; the width or 

 length along the hinge equal to about twice the length from beak to front. 

 Ventral valve ventricose, regularly arcuate from beak to front, the margin 

 of the valve forming nearly a semicircle exclusive of the hinge-extremities; 

 beak of moderate size, incurved and pointed; area moderate; a narrow, 

 rather shallow, and not distinctly defined mesial sinus marks the center of 

 the valve, and is bordered on each side by a broad, rounded plication, much 

 stronger and more elevated than the others, and which is divided along the 

 middle on the lower half of the shell by a slightly impressed line, giving it 

 the appearance of a bifurcated rib. The middle of the sinus is sometimes 

 smooth, and in some cases marked by two or three faint plications, which 

 do not extend beyond the anterior half of the shell. Besides the strong 

 plications bordering the sinus, there are from fourteen to eighteen low, 

 rounded, simple plications on each side, six or eight of which on the outer 

 end of the valve are often very obscure and sometimes obsolete. Dorsal 

 valve unknown. 



This species is very closely related to, and may possibly prove to be 

 identical with, S. hipUcatus Hall (loc. cit.), from the Burlington sandstones of 

 Iowa, but it appears to differ in not possessing the central depressed line on 

 the mesial fold, if it is safe to rely upon the evidence furnished by the 

 absence of a corresponding fold in the sinus of the ventral valve and the 

 presence of two or more obscure plications in its place. As the dorsal valve * 

 has not been observed, although several ventrals have been examined, these 

 differences cannot be positively affirmed. 



Formation and locality. — In limestones near the base of the Wah- 



