152 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY — III. 



terior in position : suborbital bones narrow, lonjjer than broad, mucli as 

 in 3/>/xosfo7«a ; fontanelle always present, usually widely open, in two 

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



Mouth rather lar<,fe, 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 oi)posite 

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

 cular apparatus moderately developeil, 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, 

 tlie 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 1-4 developed rays; anal tin short and high, 

 with probably always 7 developed rays; ventrals inserted under the 

 iHiddle 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 

 tin usually deeply forked, the lobes nearly equal. 



Sexual peculiarities not much marked, the tins higher in tlie male 

 and the anal somewhat swollen and tuberculate in the spring : br(!ed- 

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



Air-bladder with two chambers. Vertebra) in C. teres and C. nigri- 

 cans 45 to 47. 



"The fihdcton iti Catosfomus has been well described by Valenciennes 

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

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

 is a large and broad fontanelle on the upper surface of the head, separ- 

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

 The occii)ital process is, below the anterior vertebra}, enlarged into a 

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

 work on'y. The prefrontal is advanced to the anterior part of the orbit. 



