1870.] 467 
(Cope. 
PLACOPHARYNX, Cope. 
Genus novum. 
Allied to Ptychostomus, Ag. The pharyngeal teeth much reduced in 
number, only seven on the proximal half of the bone, cylindric in form, 
with a broad truncate triturating surface. These play against a broad 
crescentic chitin-like shield on the posterior roof of the pharyngeal cavity. 
Three divisions of the vesica natatoria. 
With a great superficial resemblance to Ptychostomus, the masticatory 
apparatus is different from that of any Catostomoid form known to me, and 
combines peculiarities observed in forms of true Cyprinide. The chitin- 
like shield is found in some of the latter ; it is represented in Catostomus, 
Ptychostomus and Carpiodes, by a narrow and very thin pellicle of the 
same material, frequently interrupted in the middle line. 
I know as yet but one species of the genus, 
Placopharyna carinatus, Cope. 
Species nova. 
The physiognomy and proportions of this sucker are those of the 
Pt. erythrurus or the ‘‘red horse’’ of the Western Rivers. 
The lips are large and plicate, the anterior pendent like that of the P. 
collapsus, the posterior full like that of P%. 
cervinus. Muzzle vertically truncate. Length 
of head in that of body four times; depth of 
body in same 8.66 times; scales 6—41—5. Radii 
D. XIV, V. 9. A. 7. Free margin of dorsal 
straight, not elevated anteriorly. Occipital 
region more elevated medially than in Pé. ery- 
thrurus, superior ridges well marked, with a 
special addition characteristic of this species, 
and of none other with which I am acquainted. 
This is a median longitudinal frontal ridge, ex- 
tending from the fontanelle to between the 
nasal ridges. Only the posterior extremity of 
this ridge appears in some Ptychostomi. Orbit 
longitudinally oval, 4.5 times in length of head, 
twice in interorbital width. Type, fourteen 
inches in length. 
Color in alcohol like that of other species, uniform straw or whitish 
silvery. 
The pharyngeal bones of this species are much stouter than those of 
other species of its own and greater size, ¢. g., Pt. aureolus of eighteen 
inches, where they are comparatively slight. The exteroposterior ala is 
twice as wide as the body inside the teeth is deep, and but for its short 
base and narrowed tip would do for that of a Semotilus. But while there 
are seven broad teeth without heel or cusp on the basal half, there are at 
least forty on the distal half, they becoming more compressed and finally 
like those of other allied genera. There are fourteen with truncate ex- 
Y 
