139. Posterior fontanelle (on top of skull) obliterated by the junction of the 



parietal bones in adult specimens; head 4^2 to 5 in length; eye usually 

 behind middle of head; scale count over sixty'five; pelvic fins inserted 

 below/ the posterior end of the base of the dorsal fin; Rocky Mountain 

 region Mountain Suckers 140. 



With a large posterior fontanelle; head 4 to 41/2 in length; eye usually 

 about midway in head; other characters various; generally distributed 



144. 



140. Scale count about 80 141. 

 Scale count 90 to 100 143. 



141. With less than 25 scales before the dorsal fin; brown above; Gila Basin 



J\[otolepidomyzon clar^i! (B. 6? G.) Gila Sucker 

 (Pontosteus cJar\ii (B. 6?G.) ) 

 With 28 to 50 scales before the dorsal fin 142. 



142. Body slender, about five times as long as deep; male with a red stripe 



along each side; about eight inches long; Colorado Basin 



Jsiotolepidoviyzon generosus (Girard) Mountain Sucker 



(Pantosteus generosus (Girard) ) 

 Body stouter; male with orange markings; about twelve inches long; Rio 

 Grande Valley 



Jslotolepidomyzon plebius (B. ^ G.) Rio Grande Sucker 



(Pantosteus plebius (B. 5? G.) ) 



143. Tail slender; males with reddish coloring on the sides; tributaries of the 



Colorado 



Pantosteus delphinus (Cope) Bluehead Sucker 

 Tail peduncle stout; male with an orange stripe along each side; north' 

 western species 



Pantosteus jordani Evermann 



144. Scale count more than eighty 145. 

 Scale count less than eighty 146. 



145. Fins ver>' large, the pectorals reaching to below the front end of the 



base of the dorsal fin, the pelvics reaching almost to the anal fin; upper 

 lip very thick, with five or six rows of small tubercles; lower Colorado 

 Valley 



Catostomus latipinnis B. 6? G. Flannel-mouthed Sucker 

 Fins much smaller; upper lip thinner, with about three rows of small 

 tubercles; northern states 



Catostomus catostomus (Forster) Long-nose or Northern Sucker 



146. Scale count 55 to 70; length four to five times depth; Mass. to Colorado 



Catostomus commersonii (Lacepede) Common Sucker 

 Scale count usually over 70; usually more slender, depth being about 

 five in length 147. 



147. Upper lip full and overhanging, with six to eight rov^-s of papillae; Co- 



lumbia River Basin 



Catostomus macrocherlus Girard Biglip Sucker 

 Upper lip thinner, with five or six rows of papillae; California 

 Catostomus occidentalis Ayres Sacramento Sucker 



275 



