30. CATOSTOMID^ MOXOSTOMA. 137 



sheath. Muciferous system considerably developed, a chain of tubes 

 along the supraorbital region, a branch of which extends around be- 

 hind 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, moderately long. Pharyn- 

 geal bones rather weak, much as in Erimyzon and Catostomus, the teeth 

 rather coarser, strongly compressed, the lower 5 or G much stronger 

 than the others, which are rapidly diminished in size upwards, each 

 with a prominent internal cusp. Scales large, more or less quadrate in 

 form, nearly equal in size over the body, and not specially crowded any- 

 where, usually about 44 in the lateral line (41-50) and about 12 series 

 between dorsal and ventrals. Lateral line well developed, straight or 

 anteriorly curved. Fins well developed, the dorsal inserted about mid- 

 way of the body, its first rays usually rather nearer snout than the cau- 

 dal, the number of developed rays usually about 13, but varying in dif- 

 ferent species from 11 to 17. Anal fin short and high, usually emargi- 

 nate in the male fish, probably always with 7 developed rays. Yentrals 

 inserted nearly under the middle of the dorsal ; their number of rays 

 normally 0, occasionally varying to 10; the occurrence of 10 ventral rays 

 is probably an accidental individual character, and not a permanent spe- 

 cific one. Caudal fin deeply forked, the lobes about equal, except in two 

 species. Air-bladder with three chambers. Skeleton essentially as in 

 Catostomus, the vertebra? in M. carpio 27-14. Sexual peculiarities little 

 marked, the males in the spawning season with the lower fins reddened, 

 and the anal rays swollen and somewhat tuberculate. Species very nu- 

 merous in the United States east of the Rocky Mountains. They 

 spawn in spring, running up from the rivers into the smaller streams 

 for that purpose. They are difficult to distinguish, and have perhaps 

 been unduly multiplied by authors. (/-ty|", to suck; aru^a, mouth; 

 hence, more properly Myxostoma.) 



*Lips full, strongly papillose. 



* 152. 171. p^jpaiaosMEM (Cope) Jordan. 



Body comparatively stout, the dorsal region somewhat elevated and 

 louuded, the depth being about 4 in length, the head about the same. 

 Eye rather large, high up and well back, the preorbital space being 

 longer than the other species. Top of head flat. Dorsal rays 12-14. 

 Scales rather large, 6-42-5. Lips well developed, deeply incised. 



