14 UNIVERSITY OF COLORADO STUDIES 



This group of animals, generally known as fishes, includes the sharks and 

 chimeras, the ganoid fishes, the lung fishes and true fishes. It exceeds all other 

 divisions of vertebrates in both numbers of species and numbers of individuals. 

 All types of aquatic habitats from very shallow streams to the depths of the ocean 

 are inhabited by fish. Because of the great diversity of forms represented it is 

 necessary to divide the class Pisces into several large units and many smaller 

 ones. AU of the Colorado fishes are referable to a single series, the Bony Fishes. 



Subclass TELEOSTOMI 

 The True Fishes 



Series Teleostei 



The Bony Fishes 



Bones well ossified; body naked or covered with scales; spiral valve wanting. 



Key to the Families of Fishes Found in Colorado' 



A. Ventral fins inserted well back on the abdomen, their origins barely if at all reached by the tips 

 of the pectoral fins; or ventral fins wanting. 

 B. Body without scales; adipose fin usually and barbels always present. 



Family SILURIDAE, the Catfishes, p. 15 

 BB. Body more or less completely covered with scales (one species without an adipose fin, without 

 scales). 



C. Ventral fins present. 

 D. Head without scales. 

 E. No adipose fin. 



F. Dorsal fin with 10 or more rays; fins without spines; mouth usually inferior; 

 no barbels; body usually terete. Family C^r05rOif/Z).4£, the Suckers, p. ig 



FF. Dorsal fin with g or fewer rays, without a serrate spine (native species); or 

 dorsal fin with 17 to 21 rays and a serrate spine (introduced species); barbels 

 present or absent; body often somewhat compressed. 



Family CYPRINIDAE, the Minnows and Carp, p. 31 

 EE. Adipose fin present. 



G. Dorsal fin long and high, with ig to 24 rays. 



Family THYMALLIDAE, the Graylings, p. 71 

 GG. Dorsal fin moderate, with g to 15 rays. 



Family SALMON ID AE, the Trout and Whitefish, p. 73 

 DD. Sides of the head scaled, top of the head covered with leathery plates of skin; no 

 adipose fin; lower jaw projecting; mouth somewhat superior. 



Family POECILIIDAE, the KilUfishes, p. 86 

 CC. No ventral fins; scales minute and imbedded in the skin; body long and snake-like. 



Family ANGUILLIDAE, the True Eels, p. gi 



' For the location of the various parts mentioned in this and the following keys, see Fig. 43 and the 

 glossary. In using these keys read first " A " and " AA "; if the characters of the specimen under consideration 

 are those of "A," "B" and "BB" are next to be read; if the characters are those of "AA," the two statements 

 under "AA" of equal rank with "B" and "BB" (in the above key "H" and "HH") are to be read. Pro- 

 ceed in this manner, always considering the two alternatives of the same letter which are first in rank below 

 the letter last chosen, until the name is reached. 



