1870.] 



467 



[Cope. 



PLACOPHARYNX, Cope. 



Genus novum. 



Allied to Ptycliostoiimsi, Ag. The pharyngeal teeth much rediiced 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 Ptychoatomua, the masticatory 

 apparatus is different from that of any Catostomoid form known to me, and 

 combines peculiarities observed in forms of true Cyprinidse. The chitin- 

 like shield is found in some of the latter ; it is represented in Catostomuit, 

 Ptychostomus and Carjnodes, bj' a narrow and vei-y thin pellicle of the 

 same material, frequently interrupted on the middle line. 



I know as yet but one species of the genus. 



Placnplmrynx carinaius, Cope. 



bpecies nova. 



Fif 



The physignomy and proportions of this sucker are those of the 

 Ft. erytlirams or the "red horse" of the Western Rivers. 



The lips are large and plicate, the anterior pendent like that of the P. 

 coUapsus, the posterior full like that of PL 

 cerv'inus. Muzzle vertically tx'uncate. Length 

 of head in that of body four times ; depth of 

 body in same 3. 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 Pt. ery- 

 tlivurus, 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, e.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- 



