ANALYSIS OF GENERA. 103 



Lint of Nominal Species of Catostomidce^ icith Identifications — Continued. 



ANALYSIS OF GENERA OF CATOSTOM1D.E. 



Dorsal fin short, subquadrate, with ten to eighteen developed rays: body oblong or 



elongate: gill-rakers feeble. (Catostomivce.) 

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

 developed as two separate lobes : operculum very .short : air-bladder 

 in three parts: scales large : foutanelle well developed: lateral line 



present: pharyngeal bones and teeth ordinary Quassilabia, 1. 



aa. Mouth normal, the lower lip entire or merely lobed, either tubercular or plicate. 



b. Air-bladder in three parts: lateral line continuous: fontanelie present : scales 



large, subequal. 



c. Pharyngeal bones very strong, with the lower teeth much enlarged, subcy- 



lindrical and truncate, the teeth of the upper part of the bene small 



and compressed: mouth large, somewhat oblique, with very thick 



lips Placopharyjjx, 2. 



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

 wards: mouth moderate or small, the lips usually plicate. 



Myxostoma, 3. 

 bh. Air-bladder in two parts. 



d. Lateral line interrupted or wanting : scales large (40 to i'lO in the course of 

 the lateral lir.e) : lips plicate. 

 e. Lateral line incomplete, obsolete in the young, becoming developed in the 

 adult, but always more or less interrupted: mouth small, inferior. 



MiNYTREMA, 4. 



ee. Lateral line entirely wanting : mouth somewhat oblique.. Erimyzon, 5. 

 dd. Lateral line complete and continuous : scales small, 5.5 to 115 in the course 

 of the lateral line. 

 /. Fontanelie present. 



g. Mouth very large, terminal, oblique : lips thin, nearly smooth. 



CUASMISTES, 6. 



gg. Mouth inferior, moderate or small, with thick, papillose lips. 



Catosto.mus, 7. 



ff. Fontanelie obliterated by the union of the parielal bones: mouth small, 



inferior, with thick, papillose lips, the lower jaw provided with a 



cartilaginous sheath Pantosteus, 8. 



