90 GENUS CATOSTOMUSt. 



Gill-covers. The gill-covers are large, and composed 

 of three pieces: the anterior piece small in some, as is ex- 

 emplified in the C. macrolepidotuSy and in others large, as 

 in the C communis; opening or expansion wide. 



Nostrils. The nostrils are double on each side, and 

 separated by a membrane: the largest aperture near the 

 eye. 



Eyes. The eyes in general are pretty large, a litde 

 oblong, without nictitating membrane, pupil black and 

 roundish, irides yellowish, sometimes brown, as in the 

 C. gibbqsus. 



Teeth. No teeth in the jaws; but those of the throat, 

 on each side, are composed of a range of bones, generally 

 blunt, and thick at their summits, placed in a pectinated 

 form, on an osseus, arcuated base, of which they are a 

 component part; and so netimes terminated in a hooked 

 point, as in the C. maculosiis: these teeth are enveloped 

 in a thick mass of a whitish substance, which covers the 

 throat, and supplies the place of a tongue. 



Mouth. The mouth is generally lunated; to the palate 

 is attached a membrane. 



Viscera. The intestinal canal is very much developed, 

 and it has its origin near the throat: the stomachy which is 

 simple, and without plaits and curvatures, being a continua- 

 tion of this canal, and appears to be confounded with it. 

 The intestines make a number of circumvolutions; in a 

 specimen of the C. macrolepidotus, of sixteen inches long, 

 they were three feet five inches m length. The liver is 

 deliquescent, and soon passes into oil after exposure to 

 the atmosphere. The air-bladder is subcylindric, and di- 

 vided, in most species, into two parts; in the C macrole* 

 pidotus it i^ separated into four parts. I have remarked 



