1870.1 ■*'^'^ [Cope. 



Rafinesque proposed a genus Teretuhis on the characteristic peculiarity 

 of nine ventral radii, belonging to most of the species of this genus. He, 

 however, included species of two other genera. On this account Agassiz, 

 in rearranging the suckers, imposed on it the name standing at the head 

 of this article, regarding the plicate lips as a primary character. I think 

 Rafinesque's name is to be rejected, owing to its ill application ; the more 

 as I find two species in which there are ten ventral radii. I adopt that of 

 Agassiz, though I showed, when describing the Pt. cervinus, that the 

 tricellular natatory bladder is a more distinctive feature. This becomes 

 the more obvious now that I have found a species where the lips are 

 turbercular instead of plicate. 



The following scheme will render the identification of the species more 

 simple. 



A' Lips pappillose, inferior ^ shaped. 



Head elongate, muzzle truncate. P. pappillosus. 



^^. Lips plicate. 

 «. Inferior lips infolded, ^ shaped. 



/?. Oblong species ; head one-fourth the length. 



Eye large ; D. XVI ; form compressed. P. velatus. 



Eye smaller ; D. XV ; compressed. P. collapsus. 



Eye smaller ; D. XII ; subcylindric. P. pidiensis. 



Z?/?. Fusiform species ; head one-fifth the length. 

 Muzzle conic ; mouth minute inferior. P. cokegontts. 



O.U. Inferior lips narrow, cresceirtic. 



Head one-fifth length, muzzle sub-conic. P. albtjs. 



Head long, truncate, I ; fins white. P. thalassinus. 



aaa. Inferior lips well developed, truncate posteriorly. 



/?. Compressed species. 



y. Head 4, 4.5 in length. 



S. Dorsal radii XII. 



Stout, elevated ; muzzle short, fins crimson. P. robustus. 



dS. Dorsal radii XIII. 



£. Ventral radii IX. 



Head longer, occipital region flat, muzzle truncate, eye smaller 4.5; 

 scales 5—42—4 ; scales white. P. erythrurus. 



Head shorter ; occipital region convex ; muzzle projecting, mouth in- 

 ferior, eye larger 3.5 in head ; scales black at base. 



P. MACROLEPIDOTUS. 



Head elongate, convex wnth ridges above occiput ; eye 4.5 in head ; 

 muzzle prominent, mouth inferior ; scales white. P. lachrymalis. 



es. Ventral radii X. 



Head 4 times ; muzzle conic. P. duquesnei. 



<Vld. Dorsal radii (XVII) XVIII. 



"Eye small ; depth 3.25, head 4.3 times in length." 



P. CABPIO. 

 A. P. S. — VOL. XI.— 31e 



