30. CATOSTOMID^ ICTIOBUS. 113 



** Dorsal fin short, ■with 10-18 rays. (Catostomhia;.) 

 e. Air-bladder in two parts. 

 /. Lateral liuc complete and continuous ; scales small, 55-115 in tlio 

 lateral line. 



q. Fontanelle none Paxtosteus, G3, 



gg. Fontanelle present. 



h. Mouth inferior, small, -with thick papillose Ii])s. 



Catostomus, G4. 

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

 t. Pharyngeal bones moderate, with teeth of medium size. 



Chasmistes, 65. 

 ii. Pharyngeal bones slender, with very numerous, minute teeth. 



LiPOMYZOX, 66. 

 ff. Lateral line interrupted or wanting; scales large (40-50 in a longi- 

 tudinal series). 



g. Lateral line entirely wanting Erimyzox, G7. 



gg. Lateral line more or less developed.. Minytrema, 68. 



ee. Air-bladder in three parts ; fontanelle xiresent ; scales large ; lateral 

 line comi)lete. 

 j. Mouth normal, the lower lip entire or merely lobed. 



k. Pharyngeal bones moderate, the teeth compressed, grad- 

 ually larger downw^ards; mouth moderate or small, the 



lips usually plicate Moxostoma, 69. 



kk. Pharyngeal bones very strong, with the lower teeth much 

 enlarged, subcylindrical and truncate, the teeth of the 

 upper part of the bone small and compressed ; mouth large, 

 somewhat oblique, with very thick lips. 



Placopharyxx, 70. 

 jj. Mouth singular, the upper lip not jirotractile, greatly en- 

 larged, the lower lip developed as two separate lobes, 

 pharyngeal bones and teeth ordinary Quassilabia, 71. 



59.— ICTHOBfJS Eafiuesque. 

 Buffalo-Jishes. 

 (Eafiuesque, Ichth. Oh. 1820, 55: type Amhlodon hnhalus Raf.) 



Head very large and strong, wide aud deep ; its lengtli 3i-3^ in that 

 of tlie body ; its upper surface broad and depressed. Eye moderate, 

 wliolly anterior in x>osition, the middle of the head being entirely behind 

 it ; suborbital bon6s proportionately narrow, rontanelle large, well 

 «)l)en. Opercular apparatus largely developed; the suboperculum 

 broad ; the operculum broad, strongly furrowed. Mouth very large for a 

 sucker, terminal, protracjjile forwards; the middle of the premaxillaries 

 nearly on tlie line of the middle of the eye; the posterior edge of the maxil- 

 lary extending about to the line of the nostrils. Mandible very strong, 

 oblique, placed at an angle of 45° or more when the mouth is closed, its 

 posterior end extending to beyond opposite the front of the eye, its 

 length a little less than one-third that of the head. Lips very little de- 

 veloped ; the upper narrow and smooth, scarcely appreciable; the lower 

 narrow, rather full on the sides, but reduced to a narrow rim in front, 

 Bull. Nat. Mus. No. KJ 8 



