138 TALiEONTOLOGY. 



gradually behind; posterior side apparently nan-owly rounded, and most 

 prominent above the middle; beaks nearly over the anterior margin, rather 

 pointed, depressed, and strongly incurved. Surface ornamented by numer- 

 ous, rather small, but well defined and very regular, concentric costro, about 

 equaling in breadth the furrows by which they are separated. 



Length, about 1.40 inches; height, 0.81 inch; convexity, 0.72 inch. 



The only specimen of this species in the collection has had about one- 

 third of the posterior dorsal region broken away. The general outline, how- 

 ever, can be pretty accurately inferred from the curve of the costa-. It has 

 somewhat the appearance of the anterior portion of an Allorisma; and I am 

 not quite sure that it may not more properly belong to that genus, especially 

 as it seems to have the cardinal margins of the valves inflected, as we see 

 in Allorisma. Still the curves of its costse show that it was a proportionally 

 shorter shell than is usual in that genus, and its beaks are more nearly 

 terminal than is often seen in Allorisma. 



Locality and position. — Weber Canon, Wasatch Range, Utah. Originally 

 supposed to have come from the same horizon as the Spiriferina and Avicu- 

 lopecten figured on the lower half of the same plate ; but as those shells are 

 certainly of Carboniferous age, this one, iinless it may be an Allorisma, 

 probably belonged to a higher horizon, although found loose with the other 

 forms mentioned. 



CEPHALOPODA. 



BELEMNITID^. 



Genus BELEMNITES, Auct. 

 Belemnites Nevadensis, Mci'k. 



Plato 12, figs. 7,7 a, 7 b (and 8 a, 8 6 ?). 



Guard attaining a medium or larger size, gradually tapering, appar- 

 ently not perfectly straight; section circular at the anterior end, but com- 

 pressed-elliptic near the posterior end; alveolus elongate-conical, and extend- 

 ing back nearly half the length of the guard; surface smooth. 



Length, about 3.25 inches; diameter at the anterior end, 0.60 inch; 

 larger diameter, iit 2.60 inches behind the anterior end, 0.4G inch; smaller 

 diameter, at the same point, 0.30 inch. 



