479 
MOON-EYE AND CHISEL-JAIV. 
the pharyngeal bones numerically the same as in the southern pikelets, on which 
account Professor Cope regards it as the type of a distinct family. Differing from 
the other two genera in the comparatively small size of the cleft of the mouth, and 
also in the approximate equality of the length of the jaws, this fish has no barbels, 
and only a single series of teeth in the jaws, teeth being also present on the 
pterygoid and hyoid bones, but wanting on the vomer and palatines. A further 
peculiarity is to be found in the presence of a peculiar spiral organ on the fourth 
gill-arcli; and the air-bladder differs from that of the other members of the family 
in its cellular structure, while the stomach comprises a membranous and a muscular 
portion. The fish in question is found alike in the upper Nile and in the rivers of 
Western Africa. It grows to about 2 feet in length. 
Moon-Eye and Chisel-Jaw, —Families Hyodontidaj and Pantodon tithe. 
Each of the two fishes figured in the annexed illustration is the only represent¬ 
ative not only of a genus, but likewise of a separate family; these families agreeing 
with all the remaining ones of the present section in having the pterotic bone 
normal, the base of the skull double, and four upper pharyngeal bones, all of which 
are distinct, and the third the largest and directed forwards. In the first family 
the parietal bones are united, and there are two true tail-vertebrae in front of the 
complex bone supporting the rays of the caudal fin. 
