156 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY — III, 



"Lc3 visc^re8 rappellent cenx dcs cyprinoides en g6n6ral, luais I'lntestiii, j\ cause de 

 ses uombroux rcplis, a orcore plus d'dtenflue, ... Le foie se rdsout bient6t en 

 liuile; la vossie a<?r enne est comuiiindmeiit divisd cti deux ot comuiiinifjne avec le 

 liaut de I'cesoph.'ige comrae dans no8 cyprins." — (Valen'ciexnes, Hist. Nat. dea Poiaaoiin, 

 xvii. pp. 42;j-4-J4.) 



Hvi-oMYZOx Aj^asiiz, 1*^55. — "The uame of this pemis is a mere translation of the 

 vcTiiaLiilar name of its type, the Miid-.Siicker of the West, framed iu imitation of 

 Petromyzon, but expressing its habits of living in the mud. The body is stout and 

 heavy in front, and tapers off rapidly from the shoulders towards the tail; behind the 

 dorsal it ia nearly cylindrical in form. 



"The short quadrangular head is broad and llat above, its sides are vertical. The 

 eyes are of moderate size and elliptical iu form ; the superorbital ridges are elevated 

 above the general level of the head. The mouth is inferior, and encircled by broad 

 lleshj' lips vrhich are covered with small grains or papilhc. The lower lip is bilobed. 

 The dorsal is over the ventrals, and nearer the head than the tail; its height and 

 length are nearly ecjiial. The pectorals and ventrals are broad and rounded, the anal 

 tin is slender and reaciifS the caudal. The scales are largest on the anterior portion of 

 the body. They are slightly longer than high, the ornamental concentric riJges of 

 the posterior field are broader and farther apart than those of the lateral and anterior 

 fields; those of tbo anterior and jmsterior lields rather remote, about equal in nniuber. 

 Tubes of the lateral line arising from the centre of radiation. 



"The teeth are compressed, so that their sharp edge pnyects inwards; at the same 

 time they are slightly arched inwards and inserted obliquely npon the pharyngeal 

 bones. They increase gradually in size and thickness from above downwards. The 

 masticating ridge of the teeth is transverse, compressed iu the middle and sharp; its 

 upper and lower edges are rounded and more projecting, the inner point, however, more 

 projecting than the outer one." — (Agassiz*, Am. Jouvn. Sd. Arts, 1655, p. 205.) 



C.vTOSTcftMUS Agassiz, 1855. — "I have retained the uame of Catostomus for the type 

 to which it was originally ai)plied by Forster. The bodj' is elongated, fusiform and 

 slightly compressed. The snout is short and blunt, and projects but little beyond the 

 mouth, wliich is iiift-rior. The lower jaw is short and bread. The lips are fleshy and 

 strongly bilobed below ; their surface is conspicuously granulated or papillated. The 

 bead is considerably longer than high. The dorsal is large and mostly in advance of 

 the ventrals; its length is greater than its height. The anal tin is long and slender, 

 and rcaehi's the caudal. The sexual diliVrences, so conspicuous in the genus Moxostonia 

 and I'lycii'istomus, arc hardly to be noticed iu this genus. The other lius are of moder- 

 ate size, and more or less pointed. 



"The scales are much smaller on the anterior than on the posterior portion of the 

 body; jiearly quadrangular, with rouTidrd angles, but somewhat longer than high; 

 the ornamental concentric ridges of the posterior tidd broader than those of tlu- lateral 

 and anterior fields; the radiating furrows more numerous than in llylomyzon and 

 Ptychostomus, and encroaches upon the lateral fields, where, in some species, they are 

 nearly Jis numerous as npon the anterior uiul posterior fields. Tubes of the lateral line 

 wider than in llylomyzon and Ptychc-^tomus, extending from the centre of radiation 

 to the posterior margin. 



"The pharyngeals are stout and compact, the outer margin not so spreading as 



