404 EXPLORATIONS ACliOSS THE GKEAT BASIN OF UTAH. 



The interbrancliial isthmus equals in width about four-ninths of the length of the 

 caudal fin, or a twelfth of the total length. 



The first dorsal has eight spines, and is connected with the second by a low 



The anal fin commences under the third ray of the second dorsal. 



The caudal tin forms eighteen hundredths of the total length. 



The pectoral fins extend backward to the vertical of the third ray of the second 

 dorsal fin; its median or fifth, sixth, and seventh rays are, in one specimen, on the left 

 side, abnormally dicbotomous; they are generally simple. 



The longest ventral ray equals thirteen hundredths of the total length. 



The number of rays and their arrangement are indicated by the formula — 

 1). VIII. 17; A. 12; P. 16; V.I. 4. 



The lateral line is continued in an almost straight direction to the base of the 

 caudal fin. The deflection under the end of the second dorsal is slight. The cutane- 

 ous keel in which the pores open is most developed posteriorly. 



The color does not differ from that of the nearly allied species. There are four 

 rather darker transverse dorsal bands, one under the first dorsal, two under the ante- 

 rior and posterior parts of the second dorsal, and a fourth at the base of the caudal fin. 

 The caudal fin and pectoral fins are banded or clouded with darker on the rays. The 

 spinous dorsal is punctulated with darker, especially between the anterior rays. The 

 remaining fins are hyaline. The head above is darker. 



The Potamocottus Carolina is one of the largest species of the genus, and even 

 exceeds the Potamocottus puneiulatus Gill in size. It is most nearly allied to the 

 Potamocottus Richartlsomi, but slightly differs from it in the proportions of its parts, and 

 more especially in the character of the lateral line. It is also found in a different 

 hydrographical basin, the specimens described having been obtained by Prof. S. F 

 Baird, of the Smithsonian Institution, at Maysville, Ky., in the year 1852. They are 

 now in the museum of the Smithsonian Institution, and numbered in the catalogue of 

 fishes of the museum as 2859. The largest specimen is nearly six inches long. 



Suborder EVENTOGNATHI, Gill. 

 Family CYPRINOID^E, Agass. 



Genus TIGOMA, Girard. 

 Synonymy. 



Tiooma Girard, Reaches on Cyprinoid Fishes, &c, (p. 41, 8 ep. copy) in Proceedings Academy of Natural Sciences 

 of Philadelphia, vol. viii, p. 205, 1856. 



1*be body is elongated-ovate or subfusiform in profile, and more or less com- 

 pressed. 



The scales are of moderate and nearly equal size on the different regions of the 

 body^ They extend forward to the nape and above the margin of the preoperculum. 



The head is rather small, oblong-conical in profile, with a convex or subacumi- 

 nate snout. 



The eyes are of moderate size, and situated entirely in the anterior half of tho 

 head. I he chain of suborbital bones is narrow. 



