418 EXPLORATIONS ACROSS THE GREAT BASIN OP UTAH. 



ones exceed half tlie lengtJi of tlio niaxillaiy, and are twice as long- as the internal 

 infra-maxillary ones. 



The branchiosteg-al x-ays are enveloped in a thick skin; there are eight, of which 

 the two internid are flattened and largest; the rest are slender, and rapidly decrease in 

 length. The branchiostegal membrane is deeply excavated, and is attached to the 

 tlu-oat for abont half the interval between the mental fold and the bottom of the emar- 

 gination of the membrane; the mental fold is itself midway between the emargination 

 and the lower ja^y. 



The dorsal tin commences at a tliird of the distance from the snout to the concave 

 margin of the caudal fin ; its base eqxials a fourteenth of the total length, and is scarcly 

 lialf its height. The spine is slender, and about three-fourths of the length of the 

 longest ray; its posterior margin is nearl}^ edentulous, liaving Ijut two or three tuber- 

 cles on the posterior half 



The adipose fin is elongated and fill ciform, and nearly equals in length (or height) 

 the base of the first dorsal; its base is over the penultimate I'ays of the anal fin. 



The anal fin commences at the fifty-six hundredths of the distance between the 

 snout and the concave margin of the caudal fin; it is situated one twenty-fifth of the 

 same length behind the anus. Its base is more than a fifth of the length of the fish; 

 its greatest height anteriorly (as well as can Ijo judged from llie imperfect specimens 

 before ws) is somewhat greater than an eighth of the total length, and above two and a 

 half times greater than that of the })osterior rays. 



Tlie pectoral fins have each a strong compressed spine, smooth on the external 

 margin, and armed with strong teeth directed downward on the internal one. The 

 length is equal to thirteen hundredths of the total length, and that of the first articu- 

 lated and longest ray to fifteen hundredths. The pi'ocess of the coracoid bone pro- 

 jects bej'ond the base of the pectoral spine for a distance equal to the interval between 

 the snout and orbit. The ventrals commence between the fourth and fifth tenths of the 

 length ; their length somewhat exceeds a tenth of the total. The second and third 

 rays are longest. 



The caudal fin is deeply forked, the longest ray being at least twice as long as 

 the central ones; the latter form a nintli of tlu; total length. The base of the fin is 

 convex. The rudimentary ra}'s advance conq)arati^'ely little on the superior and 

 inferior faces of the peduncle. 



The number of rays is as follows: 



I). I. 5. 1; A. 2.4; P. I. I); V. 1. 7. 



The color of the shrunk alcoholic specimen is purplish-ln'own al)Ove and silvery- 

 bronze on the sides. The free half of the anal iin is darker. 



This species is very nearly allied to several of its congeners of the western 

 streams and rivers, but a])pears to differ from all of them. From the letnlnrus ccerulcs- 

 cens (Fimelodus c(eriih'sccns Raf ) and Idalurns affiiiis (Fhiielodiis qffiitis Girard), it is 

 at once distinguishable by the fewer rays of the anal fin, there being about thirty rays 

 in that of the former and thirty-five in that of the latter. The distinction from the 

 Ictalurus ollvaceus {Pmdodns olivaceus Girard) and Icfahini.^ ruJj^es {Pimehdus vidpes 



