810 BULLETIN UNITED STATES GEOLOGICAL SURVEY. 



contains tliirteeu rays. The greatest depth is at the pectoral region, the 

 outlines contracting- to the base of the anal fin. The dorsal outline is 

 convex. The profile descends gently. The muzzle is half as long as the 

 diameter of the orbit, which enters the length of the head three times. 

 The latter enters the length without the caudal fin three and three- 

 fourths times. There is a row of short, conical teeth along the middle line 

 of the mouth, which is not on the vomer, but is on the parasphenoid or 

 axial hygal bones. Similar teeth exist in the mouth of D. dentatus. 

 The jaws may be furnished with minute teeth, or they may be wanting. 

 The scales are thin and difficult to count ; there are fifteen rows between 

 the vertebral column and the anterior anal rays. 



Measurements. 



M. 



Total length 0.195 



Length of head 0.040 



Axial length to below first dorsal ray 0.073 



Axial length to above first anal ray 0.092 



Axial length to base of external caudal rays 0.149 



Depth at orbit ." 0.030 



Depth at occiput 0.044 



Depth at first dorsal ray 9.047 



Depth at middle anal ray 0.027 



Depth at base of caudal fin 0.016 



This Herring is represented by a great number of well-preserved spe- 

 cimens, and was, next to the D. humilis, the most abundant fish of the 

 waters of the ancient Green Eiver lake-basin. It is distinguished from 

 the J>. dentatus by the larger 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 ob- 

 tained is half as large again, and much smaller than the type of Z>. den- 

 tatus. 



DiPLOMYSTUS PECTOEOSUS, Gope, sp. nOV. 



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 5 A. I. 40-44. YertebrcT. : dorsal, 16-17 ; caudal, 23. 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 th6 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 jirst 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 



