110 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY III. 



Genus MYXOSTOMA (Bafinesque) Jordan. 



Catosiomun sp. Le Sueur, and of all writers till 1855. 



Moxostoma Rafinesque, Ichthyologia Obienais, 1820, 54. (Proposed as a subgenus for 

 those species of Catoslomus with eight ventral rays and the caudal lobea un- 

 equal : type C. anisurus Raf.) 



Tereluhts Rafinesque, Ichthyologia Ohiensis, 1820, 57. (As a subgenus, to include 

 those species of Catosiomus with nine ventral rays: no type designated— most 

 of the species recorded belong to the present genus. C. aureolus Le Sueur is 

 the species first mentioned, and to this species and its relatives the name 

 Tcretulus was afterwards restricted by Professor Cope.) 



Ptycliosiomus Agassiz, American Journal of Science and Arts, 1855, p. 203. (No type 

 designated : the species mentioned are P. aureolus, P. mncrolepidotUH, P. duques- 

 nii, and P. melanops. P. aureolus has been considered the type of the genus.) 



Teretulus Cope, Journ. Ac. Nat. Sc. Phila. 1868, 236. 



Moxostoma Jordan, Manual of Vertebrates, 1876, 295. 



Myxosioma Jordan, Ann. Lye. Nat. Hist. 1877, 348. (Corrected orthography.) 



Etymology, /zi'fw, to suck ; aro/ia, mouth. 

 Type, Catofitomus anisurtis Rafinesque. 



Body more or less elongate, sometimes nearly terete, usually more or 

 less compre.ssecl. 



Head variously long or short, its length ranging from 3^ to 5J in that 

 of the body : eye usually rather large, varying from 3 to 6 times in the 

 length of the side of the head, its position high up and median or 

 rather i)Osterior : suborbital bones very narrow, always much longer 

 than broad, their width less than one-fourth that of the fleshy part of 

 the cheek : fontanelle on top of head always well open, the parietal 

 bones not coalescing. 



Mouth varying much in size, always inferior in position, the mandible 

 being hoiizontal or nearly so: lips usually well developed, the form of 

 the lower varying in different sections of the genus, usually witk a slight 

 median fissure, but never deeply incised ; the lips with transverse 

 plicae — the folds rarely so broken up as to form papillae : jaws without 

 conspicuous cartilaginous sheath : muciferous system considerably de- 

 veloped, a chain of tubes along the supraorbital region, a branch of 

 which extends around behind the eye and forwards along the suborbital 

 bones and the lower edge of the preorbital : opercular bones moderately 

 developed, nearly smooth : isthmus broad : gill-rakers weak, moder- 

 ately long, in length about half the diameter of the eye. 



Pharyngeal bones rather weak, much as in Erimyzon and Catostomus^ 



