804 PISHES — CATOSTOMID^. 



e. Lateral line entirely wanting ; mouth somewhat oblique. 



Erimyzon. 19. 

 ee. Lateral line incomplete, obsolete in the young, becoming more perfectly 

 dereloped with age, but always interrupted ; mouth inferior. 



MiNYTREMA. 20. 



cc. Air bladder in three parts ; lateral line developed. 

 f. Month 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 rather sucall Myxostoma. 21. 



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

 cylindrical and truncate ; upper teeth small and compressed ; mouth 



large, oblique Placopharynx. 22. 



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

 developed as two separate lobes ; operculum very short. 



QnASSILABIA. 23. 



Genus 14. ICHTHYOBUS. Eafinesque. 

 Amblodon, Eafinesque, Journal de Physique de Chymie et d'Histoire Naturelle, Paris, 



421, 1819 (part). 

 lotiobua, Rafinbsqub, loh. Oh., 1820, p, 55. (As subgenus of Catostomus ) 

 Ichthyohus, Agassiz, Am, Journ. Sci. and Arts, 1855, p. 195. 

 Type, Amblodon bubalns, Kafinissquk. 

 Etymology, ichthtia, tish; bom, bull or bufifalo ; i.e , buffalo-fi3h 



Head very large and strong, wide and deep, its length 3J to t'f 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 large for a 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 a little less than one- third that of the head ; lips very little developed, 

 the upper narrow and smooth, scarcely appreciable, the lower narrow, rather full on the 

 sides, but reduced to a narrow rim iu front, entirely destitute both of papillss and plicaj ; 

 jaws without cartilaginous sheath ; mnciferous system of head well developed ; isthmus 

 narrow ; pharyngeal bones in form intermediate between those of Carpiodea and those of 

 Bubalichthys, the outer surface of the arch etaudiug 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 nniformily arched as in Bubalichthys, or 

 truncate aa in Cyoleptus, 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 2| to 3^ iu the length of the body ; scales large, 

 thick, nearly equal over the body, their posterior edges somewhat serrate, the lateral 



