30. CATOSTOMID.E CHASMISTES. 131 



series. Depth 4-5 iu length ; head 4-4.J. Eye rather small, 4J to 5 

 in head. Color olivaceous; sides with brassy lustre ; belly white ; back 

 brown, with several dark cross-blotches, irregularly arranged, these 

 becoming obsolete in old individuals ; lower fins dull red, with some 

 dusky shading ; young considerably variegated, the sides spotted. Size 

 large ; maximum length about 2 feet. New York to Alabama and 

 Kansas ; abundant. Ascends streams to spawn early in spring. 



(Le Sneur, Journ. Acad. Nat. Sci. Phila. 1818, 102 : Hylomyzon nigricans Agassiz, 

 Amer. Journ. Sci. Arts, 1855, 205 ; Giiutlier, vii, 17 ; Jordan, 1. c. 1G2.) 



65. <CfiIASUIITE Jordan. 



(Jordan, Bull. Hayden's Geol. Surv. Terr, iv, No. 2, 417, 1878: type Chasm-isles liorus 

 Jor.) 



Head disproportionally large, forming more than one-fourth of length, 

 broad and flattish above ; sides of head vertical, slightly directed in- 

 wards, the breadth through the cheeks less than the breadth above the 

 eyes. Eyes small, high up, rather posterior. Mouth extremely large, 

 terminal, the lower jaw in the closed mouth being very oblique, placed 

 at an angle of about 45 degrees. The lower jaw very long and strong, 

 its length more than one-third the length of the head, nearly half the 

 length of the head in the adult, its tip, when the mouth is closed, about 

 on a level with the eye. Upper j aw very protractile. Upper lip very thin 

 (for a sucker), and nearly smooth. Snout elevated above the rest of the 

 head, the premaxillary spines usually forming a conspicuous nose. Lower 

 lip moderate, consisting of a broad flap on each side of the mandible, in 

 front reduced to a narrow rim, the surface of the lip nearly smooth, with- 

 out papillae. Nostrils large. Suborbital bones narrow, but rather 

 broader than in Catostomus. Preorbital unusually large. Mucous chan- 

 nels moderately developed. Fontanelle very large. Isthmus rather 

 narrow Pharyugeal bones weaker than usual in Catostomus, the teeth 

 generally smaller. Body rather slender, tapering pretty regularly from 

 the shoulders to the tail, but little compressed. Caudal peduncle rather 

 stout. Fins moderate ; the dorsal rays about 12 ; the anal 7. Pectorals 

 rather long, not quite reaching ventrals ; ventrals reaching vent ; anal 

 fin high, reaching caudal; caudal fin rather long, its lobes equal. 

 Scales moderate, large on the caudal peduncle, much smaller and 

 crowded anteriorly, GO-G5 in the lateral line, about 18 in a transverse 

 series from dorsal to ventrals. Sexual peculiarities unknown. Colora- 

 tion usual. Air-bladder in two parts. Size moderate or rather large. 

 , to yawn.) 



