804 FISHES—CATOSTOMIDZA. 
é. Lateral line entirely wanting; mouth somewhat oblique. 
ERIMYZON. 19. 
ee. Lateral line incomplete, obsolete in the young, becoming more perfectly 
developed with age, but always interrupted; mouth inferior. 
MINYTREMA. 20. 
cc. Air bladder in three parts; lateral line developed. 
f. Mouth normal, the upper jaw protractile, the lower lip entire or lobed, usually 
plicate. 
g. Pharyngeal bones moderate, the teeth compressed, growing gradually 
larger downward; mouth rathersmall. . .. . MyYxXosToMaA. Ql. 
gg. Pharyngeal bones very strong, with the lower teeth much enlarged, sub- 
cylindrical and truncate; upper teeth small and compressed; mouth 
large, oblique. : . : 5 . PLACOPHARYNX. 22. 
Sf. Mouth singular, the upper lip not protractile, greatly enlarged, the lower lip 
developed as two separate lobes; operculum very short. 
QUASSILABIA. 23, 
GeENUS 14. ICHTHYOBUS. Rafinesque. 
Amblodon, RAFINESQUE, Journal de Physique de Chymie et d’Histoire Naturelle, Paris, 
421, 1819 (part). 
Ictiobus, RAFINESQUE, Ich. Oh., 1820, p, 55. (As subgenus of Catostomus. ) 
Ichthyobus, AGassiz, Am. Journ. Sci. and Arts, 1855, p. 195. , 
Type, Amblodon bubalus, RAFINESQUE. 
Etymology, ichthus, fish; bous, bull or buffalo; 7.e , buffalo-fish 
Head very large and strong, wide and deep, its length 34 to ¢# in that of the body, 
its upper surface broad and depressed ; eye moderate, wholly anterior in position, the 
middle of the head being entirely behind it ; suborbital bones proportionately narrow ; 
fontanelle large, well open; opercular apparatus largely developed, the suboperculum 
broad, the operculum broad, strongly furrowed; mouth very Jarge fora Sucker, ter- 
minal, protractile forwards, the middle of the premaxillaries rather above the line of 
the middle of the eye, the posterior edge of the maxillary extending about to the line of 
the nostrils ; mandible very strong, oblique, placed at an angle of 45 degrees or more 
when the mouth is closed, its posterior end extending to beyond opposite the front of 
the eye, its length alittle less than one-third that of the head; lips very little developed, 
the upper narrow and smooth, scarcely appreciabie, the lower narrow, rather full on the 
sides, but reduced to a narrow rim in front, entirely destitute both of papille and plice ; 
jaws without cartilaginovs sheath ; muciferous system of head well developed ; isthmus 
narrow ; pharyngeal bones in form intermediate between those of Carpiodes and those of 
Bubalichthys, the outer surface of the arch standing outwards, and presenting a porous 
outer margin ; the peduncle of the symphysis is much longer proportionally, and more 
pointed thanin Carpiodes and Bubalichthys. ‘The teeth are very numerous, small, thin and 
compressed as in Carpiodes, but the lower ones are gradually larger than the upper ones ; 
their inner edge slanting outward, and not uniformily arched as in bubalichthys, or 
truncate as in Cycleptus, the innermost margin rising somewhat in the shape of a pro- 
jecting cusp; gill-rakers of anterior arch long and slender above, becoming shorter 
downward ; body heavy, robust, not especially arched above nor greatly compressed, 
the form somewhat elliptical, the depth 24 to 34 in the length of the body ; scales large, 
thick, nearly equal over the body, their posterior edges somewhat serrate, the lateral 
