74 



HIGH SCHOOL ZOOLOGY. 



resembles the Sharks in its structure, as indeed do all the 

 Ghondrostei, while the Holostei on the otlier hand a2)proach the 

 Teleosts. The skin is comparatively smooth in the Paddle-fish, 

 but, in the Sturgeon, it is provided with five rows of bony keeled 

 shields, one row on the back and two on the sides, between 

 which shields, the skin is roughened with minute teeth. 



25. Of the Holostei we have two genera, each representing a 

 separate family, Lepidosteus and Amia (Figs. 49 and 50). The 



Fig. 49. — The Garpike. Lepidosteus platystomus. J. 

 (U. S. F. C.) 



Fig. 50. — The Bowfln, or Mudfish. Amia calva. J. 

 (U. S. F. C.) 



latter at first sight looks more like a Teleost, but a closer examin- 

 ation shows the dermal bones of the head, and the unequal divi- 

 sion of the tail. The superficial resemblance is chiefly due to 

 tlie regular rows of cycloid scales, while Lepidosteus is at once 

 marked out by the oblique rows of rhombic enamelled plates, 

 which encase it in a coat of mail. It is to this (and its voracity) 

 that it owes its name of bony -pike, while it is also called garpike 

 on account of the prolongation of both jaws into a beak, a 

 peculiarity present in the marine gar-fishes (§81). In many 

 cases whei*e such complete protection is aflforded by the exo- 

 skeleton, tlie endoskeleton is incompletely developed ; such is 



