FISH OF ONTARIO. 33 



number in the others, if more are present. Head naked; body scaly in all 

 our species. Barbels two or four ; absent in most of our genera and not 

 large in any. Belly usually rounded, rarely compressed, never serrated. 

 Gill openings moderate, the membranes broadly joined to the isthmus. 

 Branchiostegals always three. Gills four, a slit behind the fourth. Pseudo- 

 branchiae usually present. No adipose fin. Dorsal fin short in all the 

 American species. Ventral fins abdominal. Air bladder usually, large, 

 commonly divided into an anterior and posterior lobe, not inclosed in a 

 bony capsule, rarely wanting. Stomach without appendages, appearing 

 as a simple enlargement of the intestines. Fishes mostly of moderate or 

 small size; very abundant both in individuals and species, and from' their 

 great uniformity in size, form, and colouration, constituting one of the 

 most difficult groups in natural history in which to distinguish genera and 

 species. Our genera are mostly very closely related, and are separated 

 by characters which, although reasonably constant, are often of slight 

 structural importance. The spring or breeding dress of the male fishes 

 is often peculiar. The top of the head and often the fins or various por- 

 tions of the body are covered with small tubercles, outgrowths from the 

 epidermis. The fins and lower parts of the body in the spring males are 

 often charged with bright pigment, the prevailing colour of which is red, 

 although in some genera it is satin white, yellowish, or black. 



Young Cyprinidae are usually more slender than adults of the same 

 species, and the eye is always much larger ; they also frequently show a 

 black lateral stripe and caudal spot, which the adults may not possess. 



The fins and scales are often, especially in specimens living in small 

 streams, covered with round black specks, immature trematodes. These 

 should not be mistaken for colour markings. 



'S>" 



Genus CAMPOSTOMA. (Stone Rollers.) 



Body moderately elongate, little compressed; mouth normal, the jaws 

 with thick lips and rudiment of a hard sheath ; premaxillaries protractile ; 

 no barbel; teeth 4-4 or i, 4-4, o, with oblique grinding surface, and a 

 slight hook on one or two teeth ; air bladder suspended in the abdominal 

 cavity and entirely surrounded by many convolutions of the long alimentary 

 canal ; peritoneum black ; pseudobranchiae present ; scales moderate ; lateral 

 line present ; dorsal nearly over ventrals ; anal short ; no spines. Herbiv- 

 orous. Sexual differences very great, the males being covered with large 

 tubercles in spring. The singular arrangement of the intestines in rela- 

 tion to the air bladder is peculiar to Campostoma among all known fishes. 



(26) Stone Roller. Stone Lugger. 



(Campostoma anomalum.) 



Body moderately stout, not greatly compressed ; the caudal peduncle 

 long and deep. Snout obtuse. Scales, 8-52 to 53-8. 



