136 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY III. 



Genus MINYTREMA Jordan. 



Miiiytrana Jokdan, Man. Vert. ed. "id, 31S, 1878. 



Caloalomus, J'tychoatomus, Moxoatoma, aud Erimyzon sp.. ACTIIOKS. 



Type, Catoatomua melanopa Rafinesque. 



Etymology, /iirtf, reduced ; rp/y/za, ajjerture, iu allusion to the imperfections of the 

 lateral line. 



Species with the form, squamation, and general appearance of Myxo- 

 .stoma, but with the air-bhidtler in two parts, as in Erimnzon, and the 

 hiteral line imperfect — in the very youDg entirely obsolete, in half grown 

 specimens showing as a succession of deepened furrows, in the adult 

 with perfect tubes, but interrupted, these tubes being wanting on some 

 of the scales, especially posteriorly. 



Head moderate, rather broad above ; mouth moderate, inferior, hor- 

 izontal, the upper lip well developed, freely protractile, the lower rather 

 sn)all, infolded, A-shaped in outline, plicate, with 12 to 20 plicte on each 

 side; lower jaw without cartilaginous sheath; eye moderate, rather 

 high up, placed about midway of the head. Suborbital bones consid- 

 erably developed, not very much narrower than the fleshy portion of 

 the cheek below them, the posterior suborbital concavo-convex, about 

 twice as long as deep, sometimes divided, the anterior somewhat deeper 

 than long, often divided into two, sometimes united with the preoibital, 

 which is well developed and much longer than bioad. The number and 

 form of these bones, except as to their depth, are not constant in the 

 same species, and do not afford specific characters. Oi>ercular bones well 

 developed, not much rugose. Foutanelle evident, rather huge. Gill- 

 rakers rather long, in length about half tlu' diameter of the eye. Isth- 

 mus moderate. Pharyngeal bones essentially as in Myxostoma. 



IJody rather elongate, subterete, becoming deep and rather compressed 

 with age. Scales rather large, nearly equal over the body, the radiating 

 furrows not specially marked. Lateral line as above described, iuter- 

 iMjjted in the adult, but with perfect tubes, imperfect in partly grown 

 specimens, entirely obsolete in the young. Scales in a longitudinal 

 series 14 to 17 in number, 12 to 14 in a transverse series from dorsal to 

 ventrals. 



Dorsal lin rather short and high, with about 12 developed rays, be- 

 ginning rather nearer the snout than the base of the caudal. Pectoral 

 tins moderate, not reaching ventrals, the latter not to vent. Ventrals 

 rather in advance of Iho middle of the dorsal, their rays normally 9, 



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