162 Bulletin 41, United States National Museum. 



Branchiostegala 3 ; gill membranes more or less united to the isthmus, 

 restricting the gill openings to the sides ; gills 4, a slit behind the fourth ; 

 pseudobranchiiw present. Scales cycloid, large or small. Laterg,l line 

 decurved, sometimes -wanting. Head naked ; fins not scaly. Dorsal fin 

 comparatively long (of 10 to 50 rays), without true spine ; anal fin short; 

 caudal fin more or less forked; ventrals abdominal, with about 10 

 rays; pectoral fins placed low, without spine; no adipose fin; belly not 

 serrated. Alimentary canal long. Stomach simple ; no pyloric ca'ca. 

 Air bladder large, divided into 2 or 3 parts by transverse constrictions, 

 not surrounded by a bony capsule. Genera 14; species about 60; in- 

 habiting the fresh waters of North America ; 2 species iu Eastern Asia ; 

 ascending streams in large numbers in the spring. They are not much 

 valued as food fishes, the flesh being flavorless and full of small bones. 

 (Cyprinid.e, group Catostomina, Giinther, Cat., vii, 12-24.) 



a. Dorsal fin elongate, its developed rays 25 to 50 in number; air bladder in 2 parts. 



ICTIOBIN^ : 



h. Fontanelle present ; body ovate ; scales large, 

 c. Dorsal rays 24 to 33. 



(Z. Mouth large, more or less terminal, protractile forward ; lips thin ; pharyngeal 

 bones and teeth moderate ; large species, dark iu color. Ictiobus, 88. 



dd.. Mouth smaller, inferior, protractile downward. Pharyngeal bones narrow, 

 with the teeth thin and weak; smaller species of pale coloration. 

 CYCLEPTINiE : OAanoiiES, 80. 



\>h. Fontanelle obliterated by the union of the parietal bones ; body elongate. 

 e. Mouth small, inferior, with thick, papillose lips ; scales rather small. 



CATOSTOMINiE: ClCLEPTUS, 90. 



no. Dorsal fin short, with 10 to 18 developed rays. 

 /. Air bladder in 2 parts. 



g. Lateral line complete and continuous ; scales Buiall, 55 to 115 in the lateral line. 

 h. Fontanelle nearly or quite obliterated in the adult by the union of the parietal 

 bones ; jaws with hard sheaths ; posterior division of air bladder slender. 



Pantosteus, 91. 

 Mh. Fontanelle broad and evident at all stages of growth; posterior division of air 

 bladder broad, 

 i. Nuchal region without hump, the interneural spines normally developed. 

 j. Mouth inferior, small, with thick papillose lips. Catostomvs, 92. 



jy. Mouth very large, terminal, oblique ; lips thin and nearly smooth; 

 pharyngeals weak, with numerous small teeth. Chasmistes, 93. 

 ii. Nuchal region with high sharp-edged hump, formed by the greatly en- 

 larged and expanded interneural spines. Xykauciien, 94. 

 33. Lateral line iuterrui)ted or wanting ; scales large (40 to 50 in longitudinal series). 

 A-. Lateral line entirely wanting. Euimyzon, 95. 

 /./>■, Lateral line more or less developed, especially in the adult. Minytrema, 9G. 

 ff. Air bladder in 3 parts ; fontanelle present ; scales large ; lateral line complete. 

 I. Mouth normal, the lower lip entire or merely lobed, the upper protractile. 



TO. Pharyngeal bones moderate, the teeth compressed, gradually larger down- 

 ward; mouth moderate or small, the lips usually plicate. Moxostoma, 97. 

 mm. Pharyngeal bones very strong, with the lower teeth much enlarged, sub- 

 cylindrical and truncate, the teeth of the upper part of the bone small 

 and compressed ; mouth large, somewhat oblique, with very thick lips. 



Placopharynx, 98. 

 IX. Mouth singular, the upper lip not protractile, greatly enlarged, the lower lip 

 developed as 2 separate lobes ; pharyngeal bones and teeth ordinary. 



Lagociula, 99. 



