76 THE WASATCH AND BRLDGER FAUN^. 



Measurements. 



IL 



Total length I'JS 



Length of head 040 



Axial length to below first dorsal ray 073 



Axial length to above first anal ray 092 



Axial length to baae of external caudal rays 149 



Depth at orbit 030 



Depth at occiput 044 



Depth at first dorsal ray 047 



Dei>th at middle anal ray 027 



Depth at base of caudal tin 016 



This Herring is repi'esented by a great number of well-preserved spec- 

 imens, and was, next to the Z>. humilis, the most abundant fish of the 

 waters of the ancient Green River Lake basin. It is distinguished from the 

 D. dentatus by the large number of anal and smaller number of dorsal radii, 

 and by the shorter head and relatively more slender body. The specimen 

 measured represents the average size; the largest obtained is half as large 

 Again, and much smaller than the type of D. dentatus. 



From Twin Creek, Wyoming. 



DiPLOMYSTUS PECTOEOSU8 CopO. 



Bulletin U. 8. Geol. Surv. Terrs., 1877, p. 810. 



Plat* X, fig. 3. 



This Clupeoid is represented by small specimens of a deeper form than 

 that seen in the two preceding species. It is also characterized by a smaller 

 number of dorsal radii than either of them. Formula: D. I. 8-9; A. I. 

 40-44. VertebriB: dorsal, 16-17; caudal, 22. The greatest depth is in 

 the pectoral region, and enters the length minus the caudal fin a little less 

 than three times. The outlines contract from the ventral fins, and the anal 

 region is longer than the abdominal. The eye is a little more than one- 

 fourth the length of the head, and the latter enters the total minus the 

 ■caudal fin three and a half times. The ventral fins are small, and commence 

 well in advance of the line of the dorsal. The last dorsal ray is nearly 

 above the first anal ; the caudal is deeply forked. As in the two preceding 

 species, the neural spines in front of the interneurals present a laminar 

 antero-posterior expansion. The dorsal scuta are furnished in the D.pectoro- 

 3US with an especially prominent median keel. 



