no FIELD COLUMBIAN MUSEUM ZOOLOGY, VOL. III. 



A boat is then anchored some distance from the shore at the edge of 

 the vegetation or of the deep water and into it the net is pulled. The 

 species of this genus evidently spawn in the late summer or fall. 

 Those taken the latter part of May had the ovaries very little devel- 

 oped. The individuals of the species of large size belonging to this 

 genus seldom exceed a foot in length. 



KEY TO THE SPECIES OF CHIROSTOMA. 



a. Scales large, fewer than 45 in the lateral line, edges of scales 

 entire, vertebrae usually fewer than 40. Species of small size. 

 {Eslopsarum. ) 



b. Mouth small very oblique; snout short, 4 in the length of head; 

 base of anal equal to or slightly longer than head; anal rays 16 to 18. 

 Teeth very minute; scales with entire edges, 37 or 38 in the lateral 

 line. JORDANI. 



bb. Mouth larger, less oblique; snout longer, 2^ to 3| in the 

 length of the head; base of anal equal to or shorter than the head. 



c. Origin of spinous dorsal over tips of ventrals, midway 

 between base of caudal and nostril. 



d. Body robust, its depth 4^ in the length of the body; base of 

 anal i in the head, its rays i6or 17; scales 38 to 40-11. Teeth large, 

 sharp, in two definite rows in each jaw. Gill-rakers long and slender, 

 3-)-! i 14 on first arch. ARGE. 



dd. Body slender, its depth 6 in the length of the body, scales 

 42-10; anal rays 15; gill-rakers long and slender, 4+17 on the first 

 arch. BARTONI. 



cc. Origin of spinous dorsal over middle of ventrals, being 

 nearer tip of snout than base of caudal by a distance equal to the 

 diameter of the eye; base of anal i| in the head, its rays 13 or 14; gill- 

 rakers 4+18=22. Teeth very small. ATTENUATUM. 



ccc. Origin of spinous dorsal over space between tips of ventrals 

 and origin of anal fin, midway between base of caudal and posterior 

 margin of orbit. Base of anal fin equals length of the head, its rays 

 20. Teeth large, in a single row, except near tip of upper jaw where 

 there are a few large canine-like teeth; scales 42-12; gill-rakers 4+13. 



LABARC^E. 



aa. Scales smaller, more than 45 in the lateral line; edges of the 

 scales usually crenate; vertebrae more than 40. 



e. Scales entire; base of anal about if in the length of the head, 

 its rays 13 to 19; snout 3 to 3^ in the length of the head. (Chirostoma.') 



f. Origin of spinous dorsal nearer tip of snout than base of 

 caudal. 



