HIGH SCHOOL ZOOLOGY. 53 



4. Those characteristics which the individuals of a species 

 possess ill coniinon, and wliich serve to distinguish them from 

 individuals of another species are expressed together with th ir 

 habitat, or range of geographical distribution, in a specific 

 diagnosis ; as examples the following diagnoses of the species 

 which occur in Ontario may be copied from a x'ecognized 

 authority : — 



A. nehtdosics (Le Sueur) Gill. 



Colour dark yellowish-brown, more or less clouded, sometimes yel- 

 lowish, sometimes neai-ly black. Body rather elongate ; depth contained 

 4 times in length (measured to the base of the caudal fin). Anal fin , 

 usually with 21 or 22 rays, its base contained 4 times in the length of 

 the body. Dorsal fin inserted rather near the adipose than the end of 

 the snout. Upper jaw usually longer than lower. Humeral process 

 more than half the length of the pectoral spine. Length 18 inches. 

 Great Lakes, Ohio Valley, and Eastward. The common bullhead or 

 horned pout of the North and East, abundant in every pond and stream, 

 also introduced into the rivers of California, where it has rapidly multi- 

 plied. 



A. natalis (Le Sueur) Jordan. 



Yellowish, greenish or blackish. Body more or less short and chubby, 

 sometimes extremely obese (var. natalis), sometimes more elongate 

 (var. Uvidus). Head short and broad. Mouth wide, the jaws equal 

 (var. lividii-'i), or the upper jaw longest (var. ciqn-eus). Anal rays 24-27. 

 Great Lakes to Virginia and Texas ; generally abundant. Extremely 

 variable, and running into several varieties, 



A. vulgaris (Thompson) Nelson. 



Dark reddish-ljrown or blackish. Body moderately elongate ; depth 

 4-5 in length. Head .3-4. Barbel long. Mouth wide. Head longer 

 than broad, rather narrowed forward. Profile rather steep, pretty 

 evenly convex. Dorsal regions more or less elevated. Lower jaw 

 strongly projecting. Anal rays 20. Length 18 inches. Vermont to 

 Minnesota and southward ; rather common. 



It will be observed that the distinguishing features of these 

 three species are to be found in the shape of the body, the length 

 of the anal fin, and the relative length of the jaws. 



