114 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY III. 



auotlier tliaii in tlio preceding genera, und arcbed inward as in Moxostonia, the inner 

 edge of the lower ones square, its inner margin rising into a broad ensp in the middle 

 and npner teetb." — ( JmfnV;an Jonrn. Svi. Arts, xis, p. 2015.) 



TERETi-i.fS Cope, 1868. — "The essential character of this genns is the division of 

 the natatory bladder into three chambers, while Catostorans and all Cyprinidaj, exhibit 

 but two. Tliis feature is accompanied by plicate lips, as Agassiz has indicated, and 

 nine rays to the ventral tin, already pointed out by Eafinesque. The species are the 

 largest scaled of the typical suckers. Le Sneur and Vale^nciennes have pointed out 

 the generic features in the /'. viacrolepidotim ; Prof. Baird informs me that it occurs 

 in rt. florvaUs Rd., aud I find it in P^ cervinus and I'l. duquexnii. It no doubt exists 

 also in the Pt. aureolas. Other species descrilied by Bainl and Girard from the South- 

 west probably possess it. 



"It is difficult to assign a name to this g(^nus. Raliiiesquo proposes it upon unten- 

 able characters, and includes with it species of Moxostonia and Catostomus. Agassiz 

 purged it of these elements, but did not express its essential character, apparently rely- 

 ing on the plicate lips. I have taken the older name, leaving for others the final 

 decision."— (JoMJ-nai Acad. Nat. Sci. Pliila. 180H, p. 230.) 



Ptychostomus Cope, 1870. — '• The development of the ii|)H furnish important diag- 

 nostic indications in thi*genus. In tho*e most nt arly allied to Moxostoma,tho inferior 

 lip resembles that of that genus in being narrower and deeply incised, emargiuate 

 posteriorly forming a figure V with the apex forwards, at the same time the superior 

 lip is very thin and often narrow. Such species are shorter, and tend to a great de- 

 velopment of dorsal fin. Others of tiiis type are more elongate. Some. species of both 

 are distinguished by their very prominent couio muzzle and minute, inferior mouth, 

 reminding one of the Carpiodes. In one species the lips are papillose instead of plicate. 

 In some species, the mouth is very projectile, in others scarcelj' so at all. 



" Rafinesqiie proposed a genus Tcretulus on the characteristic peculiarity of nine ven- 

 tral radii, belonging to most 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 ton ventral radii. I adopt that of 

 Agassiz, though I showed, when describing the /*/. cervinus, that the tricellular nata- 

 tory bladder was a more distinctive feature. This becomes the more obvious now that 

 I liave found a species where the lips are tubercular instead of plicate." — (/Voo. Jhi. 

 Philos. Soc. Phila. p. 4G9.) 



MOXOSTOMA Jordan, 1H7(!.— •• Doi.sai modtrale, of 11 to 20 rays : air bladder in three 

 parts: lips usually plicate: lateral lino very distinct: pharyngeal teeth numerous and 

 all small, of tho usual type, the bones slender" (in comparison with those of I'lacopha- 

 rynx).—iMan. Vert. E. U. S. p. 292.) 



MoxoSTOMA Cope & Jordan, 1877. — " Body oblong or elongate, with a short sub- 

 qnadrate dorsal fin of 10 to 17 developed rays: air bladder in three parts : lateral line 

 present: fontanelle present: scales large, subequal : pharyngeal bones not especiiiUy 

 enlarged, the teeth of the usual type." — (Jokdan, Proc. Acad. Nat. Sci. Phila. 1877, p. 

 Jfl.) 



