Jordan a/n/ F.Termann. — Fishes of JVorth America. 109 



tbo males in spring almost black. Size large. Length 2^ feet. Missis- 

 sippi Valley; rather common in large streams. A singular and interest- 

 ing lish. (elongatus, elongate). 



Caloslonms elo7igatiis, Le SuEUR, Jour. Ac. Xat. Sci. Phila., I, 1817, 103, Ohio River. 



Sckrognallms ehngalns, GiiNTiiER, Cat., vii, 23, 1868. 



Ci/rlcplnii elonijafm, Jordan & Gilbert, Synopsis, 121, 1883. 



Cycleptns nigrescens, Rafinesque, Jour. Phys., 1819, 421, Ohio River. 



AvModoH uiga; Kafjnesque, I. c, 421, {descriptioa insufficient; at second liaud), Ohio River. 



91. PANTOSTEUS, Cope. 

 (Mountain Suckers.) 



Pantosteiis, Cope, Lieut. Wheeler's Expl. W. 100th Mer., v, 673, 1876, {platyrhy>ic}iu.<). 



Head rather small, 4 to 5 times in length of body, flattish and rather 

 broad above, anteriorly somewhat pointed. Eye rather small, usually 

 behind the middle of the head. Suborbital bones narrow. Bones of head 

 rather thick, the 2 parietal bones in the adult more or less united, 

 partly or Avholly obliterating the fontanelle, which, however, is evident 

 in the young. Mouth rather large, entirely inferior; each jaw with a 

 more or less developed cartilaginous sheath. Upper lip broad, papillose, 

 with a rather broad free margin and 2 or more series of tubercles. Lower 

 lip largely developed, with a broad free margin deeply incised behind. 

 Pharyngeal bones and teeth essentially as in Catostomus. Isthmus broad. 

 Body elongate, subterete, little compressed. Scales quite small, 80 to 105 

 in the course of the lateral line, and 30 to 35 in a cross series between 

 dorsal and ventrals, usually more or less reduced in size and crowded for- 

 ward, as in Catostomus, Lateral line well developed, straightish. Fins 

 generally rather small. First ray of dorsal usually about midway of 

 body, its rays few, 9 to 12 in number. Ventrals inserted under posterior 

 part of dorsal, the rays 10 or 9; anal short and high, with 7 developed 

 rays. Caudal rather shallow emarginate. Pectorals well developed. 

 Air bladder with 2 chambers, the posterior chamber very slender. Size 

 rather small. Rocky Mountain region, mostly in rocky brooks in the 

 arid district. The genus is close to Catostomus and may be inseparable 

 from it, as in 3 species of Pantosteus the fontanelle never quite disappears, 

 retaining through life the characters of the young of other species of 

 Pantosteus. This indicates the probability that Pantosteus is a modified 

 descendant of specieB of Catostomus. {navr, all; oa-toi', bone.) 



a. Fontanelle entirely obliterated in tlio adult. 



h. Scales of back very much enlarged, there being less than 20 between dorsal fin and 

 nape, along the median line; about 75 scales in lateral line. Head ver.v broad, and 

 flattish .above. Gila basin. arizon.t;, 271. 



66. Scales of back not notably enlarged, there being 30 to 50 before dorsal. 



c. Scales moderate, 80 to 90 ; mouth and lips moderate; dorsal rays usually 9. 



d. Head short and small, nearly 5 in length ; body slender. Utah basin. 



QENEROSrs, 272. 

 dd. Ile.ad rather large, about 4^ in length; body stout. Rio Grande. 



pi.EnEU'S, 273. 

 cc. Scales very small, 90 to 100 in lateral line, usually about 9.">; mouth large, with very 

 full lips; head short; tail Blender; dorsal rays 9 to 12. 



e. Caudal moderate, shalIow-fork('<l, its lobes shorter than head; fins low. Colo- 



rado basin. delpiiinus, 274. 



