216 



LOWER VERTEBRATES. 



Along the entire eastern and gulf states of North America, and in the great rivers 

 and lakes of the interior, are found a couple of fishes of a peculiar build and with 

 certain salient characteristics of the pharyngeal bones. The body is much compressed 

 and quite elevated, and rather protracted forward at the front of the back, and the 

 lower pharyngeal bones are enlarged and joined together at the middle, forming 

 a single triangular piece which is studded by teeth, reminding one of the cobble- 

 stones which in olden times were used for paving the streets of cities. These bones 

 are often to be seen in collections of curiosities. The species of the type so distin- 

 guished represent two genera, one confined to the salt water and the other to the 

 fresh. Drum is the common name given to both forms. 



The drum of the salt water (^Pogonius chromis) is distinguished by the develop- 

 ment of numerous little thread-like appendages or barbels from the lower jaw, and the 



Fig. 122. — Pogonias chromis, drum-fish. 



tail fin is emarginated or subtruncate. Its appearance is quite different according to 

 age; when young it has four or five broad, vertical, dark bars, but with age these dis- 

 appear, leaving the old uniformly colored gray silvery. The fins are also relatively 

 larger in the young than in the full grown. The species is by far the largest of the 

 American representatives of the family. It occasionally attains a weight of nearly one 

 hundred pounds, but of course this is very unusual, and the average is perhaps some- 

 where about twenty pounds. The species is noted for the depth of the sounds, 

 somewhat resembling those from a mufiled drum, which it makes and which have ob- 

 tained for it the name of drum-fish. This drumming sound is common to a large 

 proportion of the species of the family, but is much deeper in the drum-fishes of the 

 sea as well as fresh waters, than any of their relatives. It is said to be due, partly at 

 least, to the action of the pharyngeal bones grinding upon each other. 



The drum-fish is especially addicted to shell-fishes, and particularly mussels, clams, 



