GENUS MYXOSTOMA. 113 



and lips, although the species of Minytrema was inadvertently included 

 in it. The most important generic feature, the tricellular air bladder, 

 was first noticed by Professor Cope. 



I have seen fit to change the orthography of the name from Moxostoma 

 to Myxostoma, in accordance with its apparent etymology. This change 

 is rather desirable from the fact that it tends to avoid confusion, the 

 name Moxostoma having been commonly used in connection with a 

 different genus. 



The genus Myxostoma contains two well marked sections, typified 

 respectively by M. velatum and M.macrolepidotum, and characterized by 

 the form of the mouth and lower lip : that of M. velata being as in the 

 genus Erimyzon; that of M. macrolepidotum being of the character most 

 common in this genus. 



Generic Characterisations. 



MOXOSTOMA Rafiuesque, 1820. " Body oblong, compressed ; head compressed, eight 

 abdominal rays, dorsal fin commooly longitudinal ; tail commonly unequally forked." 

 (Ic'htJiyoIoyia Ohiensis, p. 54.) 



TERETULUS Rafinesque, 1820. " Body elongate cylindrical or somewhat quadrangu- 

 lar, 9 abdominal rays, dorsal fics commonly small; tail equally forked. An exten- 

 sive submenus, to which belong all the following species of Le Suenr: C.aureolus, C. 

 macrotyidotus, C. lonoirostrum, C. nigricans, C. vittalus, C. maculosus, C. sucetta, besides 

 the C. teres and C. oblongus of Dr. Mitchill." ( left. Oh. p. 57.) 



PTYCHOSTOMUS Agassiz, 1855. "In resptct to form of body and the structure and 

 position of the fins, this genus does not differ from Catostomus proper, but may be 

 distinguished, by the following structural peculiarities. The lips are marked by trans- 

 verse ridges or folds, and hardly bilobed below ; they are not papillated as in Catosto- 

 mus proper. The generic name of this type is derived from this character of the lips 

 The head is shorter and stouter. The dorsal is longer than it is high, but in the males, 

 it is longer in proportion than in the females. The anal of the male is also broader 

 than that of the female, and its lower margin lobed, while in the female it is trape- 

 zoidal and narrow. 



" The ecales are as large on the anterior as on the posterior region of the body ; their 

 ver.ical diameter about as great as the longitudinal, so that the scales are nearly quad- 

 rangular, with rounded edges; the ornamental concentric ridges not longer nor broader 

 upon the posterior than upon the lateral and anterior fields ; the radiating furrows few,, 

 only one or two in the posterior field and one on each side limiting that field from the 

 lateral fields; those of the anterior field are more numerous, and yet not crowded; 

 Tube of the lateral line arising in the centre of radiation or farther back upon the 

 posterior field. 



" The pharyngeals are strong, their entire edge spreading like a wing, and that 

 spreading margin is separated from the symphysis by a deep emargination. The 

 teeth increasing rather rapidly in size from above downwards, are more apart from one 

 Bull. N. M. No. 128 



