38 Field Columbian Museum— Zoology, Vol. V. 



bb. Air bladder not surrounded by alimentary page 



canal. 

 c. Intestinal canal elongate, usually more 

 than twice the length of the body, and with 

 several convolutions; peritoneum usually 

 black, 

 d. Scales small, more than 55 in the lateral 

 series; lateral line complete. 



e. Gill rakers long and slender, more than 



60 on the first gill arch Xystrosus 43 



ee. Gill rakers short, less than 60 on the 



first gill arch Algansea 44 



dd. Scales large, 35 to 45 in the lateral series. 



f. First (rudimentary) ray of dorsal fin 

 slender, and attached firmly to the first 



developed ray Hybognathus 48 



ff. First (rudimentary) ray of dorsal fin blunt, 

 enlarged and connected to first dorsal ray 



by a membrane Pimelocephales 50 



cc. Intestinal canal short, less than twice 

 length of the body, and with usually one 

 convolution; peritoneum usually pale, 

 g. Teeth in the main row 5-5 or 4-5 (3-3 in 

 Stypodon) ; usually 2 teeth in the lesser 

 row. 

 h. Abdomen behind ventral fins transversely 

 rounded, the scales passing over it, the 

 edge not forming a scaleless ridge; base 

 of anal fin generally short; body little 

 compressed; lateral line but slightly be- 

 low axis of the body, 

 i. Teeth subconical, scarcely hooked, sharp 

 edged, wide apart; the long limb of the 

 pharyngeal bone elongate ; body elongate ; 

 mouth large. 



j. Teeth 3-3, scales 35 Stypodon 51 



jj. Teeth 2, 4-5, 2 ; scales 80 to 90 Ptychocheilus 52 



ii. Teeth compressed, strongly hooked; the 

 pharyngeal bones of the usual form. 

 k. Caudal peduncle slender and elongate; 

 the caudal fin forked, its basal rudi- 

 ments much developed; scales very 

 small, 83 to 87 in lateral series; head 



