152 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY III. 



terior in position : suborbital bones narrow, longer than broad, much as 

 in Myxostoma: fontanelle always present, usually widely open, in two 

 species reduced to a narrow slit, but never wholly obliterated. 



Mouth rather large, always inferior, and sometimes notably so ; the 

 upper lip thick, protractile, papillose ; the lower lip greatly developed, 

 with a broad free margin, deeply incised behind, so that it forms two 

 lobes, which are often more or less separated : mandible horizontal, 

 short, not one-third the length of the head and not reaching to opposite 

 the eye: lower jaw usually without distinct cartilaginous sheath : oper- 

 cular apparatus moderately developed, not rugose : pharyngeal bones 

 moderately strong, the teeth shortish, vertically compressed, rapidly 

 diminishing in size upwards, the upper surface of the teeth nearly even, 

 or somewhat cuspidate. 



Body oblong or elongate, more or less fusiform, subterete, more or 

 less compressed. 



Scales comparatively small, typically much smaller and crowded an- 

 teriorly, the number in the lateral line ranging from about 50 to 115, 

 the number in a transverse series between dorsal and ventrals from 

 ]5 to 40: lateral line well developed, straightish, somewhat decurved 

 anteriorly. 



Fins variously developed: dorsal with its first ray nearly midway of 

 the body, with from 9 to 14 developed rays ; anal fin short and high, 

 with probably always 7 developed rays ; ventrals inserted under the 

 middle or posterior part of the dorsal, typically with 10 rays, in one sub- 

 genus usually 9, the number often subject to variation of one ; caudal 

 fin usually deeply forked, the lobes nearly equal. 



Sexual peculiarities not much marked, the fins higher in the male 

 and the anal somewhat swollen and tuberculate in the spring : breed- 

 ing males in some species with a rosy or orange lateral band. 



Air-bladder with two chambers. Vertebra in G. teres and C. nit 

 cans 45 to 47. 



" The skeleton in Catostomus has been well described by Valenciennc 

 (XVII. p. 433). It is distinguished by the comparative want of solidity, 

 certain bones consisting merely of a network of osseous matter. Ttu 

 is a large and broad foutanelle on the upper surface of the head, sepai 

 ating the parietal bones, and leading directly into the cerebral cavity. 

 The occipital process is, below the anterior vertebra, enlarged into 

 bladder-like swelling, which is not solid, but consists of a delicate net 

 work only. The prefrontal is advanced to the anterior part of the orbil 



