1870.] 469 
[Cope. 
Rafinesque proposed a genus Jeretulus 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 obvicus now that I have found a species where the lips are 
tubercular instead of Plicate. 
: The following scheme will render the identification of the species more 
simple. 
A. Lips pappillose, inferior, 4 shaped. 
Head elongate, muzzle truncate. 
AA. Lips plicate. 
@. Inferior lips infolded, 4 shaped. 
B. Oblong species ; head one-fourth the length. 
Eye large; D. XVI; form compressed. 
P. PAPPILLOSUS. 
P. VELATUS. 
Eye smaller; D. XV ; compressed. P. COLLAPSUS. 
Hye smaller; D. XII; subcylindric. P. PIDIENSIS. 
#3. Fusiform species ; head one-fifth the length. 
Muzzle conic ; mouth minute inferior. P. COREGONUS. 
aa. Inferior lips narrow, crescentic. ; 
Head one-fifth length, muzzle sub-conic. P. ALBUS. 
Head long, truncate. 3; fins white. P. THALASSINUS. 
aaa. Inferior lips well developed, truncate posteriorly. 
&. Compressed species. 
y- Head 4, 4.5 in length. 
6. Dorsal radii XII. 
Stout, elevated ; muzzle short, fins crimson. P. ROBUSTUS. 
60. Dorsal radii XIII. 
é. 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 with ridges above occiput; eye 4.5 in head; 
muzzle prominent, mouth inferior ; scales white. P. LACHRYMALIS. 
"ee. Ventral radii X. 
Head 4 times ; muzzle conic. P. DUQUESNEI. 
600. Dorsal radii (XVII) XVIII. 
"ee Eye small; depth 3.25, head 4.3 times in length.”’ 
P. CARPIO. 
A. P. S.—VOL. xI.—315E 
