110 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY III. 



Genus MYXOSTOMA {Rafinesqne) Jordan. 



CatoHtomua hj). Le Sueur, anil ol all writers till IHSf). 



MoxoHtoma Rafinesquk, Iolitliy<ilogi,a Obienais, 1820, 54. (Proposed as a Bubgonus for 

 tbo.se sj)ecie8 of CaloHtomuH witb eigbt ventral rnys and tbe candal lobes un- 

 equal : typo C. amsurus Raf.) 



Terclithii Kakinesque, Icbtbyolofria Obiensis, 1820, 57. (As a euhgetiiiH, !(» iucluilo 

 those ppecies of Catontomiis witb nine ventral rays: no type designated— most 

 of the species recorded belong to tbe present genus. C. aitreolua Lc Sueur is 

 tlie species Grst mentioned, and to this species and its relatives tbe name 

 TcrttuUm was afterwards restricted by Professor Cope.) 



Ptychostomns Agassiz, American Journal of Science and Arts, 185.5, p. 203. (No type 

 designated : tbe species mentioned are P. aureolm, P. mncrohpidotun, P. duques- 

 nil, and P. melanops. P. aureolua has been considered tbe type of tbe genus.) 



Teretuhix Copk, .fourn. Ac. Nat. Sc. Pbila. 18(i8, 236. 



Moxostoma Jordan, Manual of Vertebrates, IriTG, 295. 



Alyxostoma Jordan, Ann. Lye. Nat. Hist. 1877, 348. (Corrected ortbograpby.) 



Etymology, /ii'iu, to suck ; aru/ia, moutb. 

 Type, Cutmtomaa nniauruH Kafioesquc. 



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

 less cotn pressed. 



Uead vnrionsly long or short, its k'n;itli ranging i'rom 3.^ to 3.^ in that 

 of llic l»ody : eye usually rather large, varying from 3 to 6 times in tbe 

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

 rather posterior: suborbital bones very narrow, always much longer 

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

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

 bones not coalescing. 



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

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

 tbe lower varying in ditterent sections of the j;enus, usually with a slight 

 median tissurc, l»ut ncNcr dfcply incised ; the li{)s with transverse 

 plicai — the Iblds rarely so broken up as to form papillue : jaws without 

 consi)icuous cartilaginous sheath : muciferous system considerably de- 

 veloped, a chain of tubes aU)ng the supra()rbital region, a branch of 

 whitth extends around behind the eye and forwards along the suborbital 

 bonesand tbe lower edge of the preorbital : op<icular bones moderately 

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

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



Pharyngeal bones mtber weak, much as in Erimyzon and CatostomtLS^ 



