152 FIRST LESSONS IN ZOOLOGY. 



fishes have in places surrived by reason of their vigor, fe- 

 rocity, big jaws and teeth, as well as their thick, close-set, 

 enamelled scales. 



While one branch of the ichthyic tree of life ended in the 

 garpike, a twig from this branch is represented by the mud- 

 fish. 



The mnd-fish of Western and Southern waters (Amia 

 calva) is a connecting link between the Ganoids and com- 

 mon or bony fishes. It bears a general resemblance to and 

 is about the size of a small bass. Its tail is less uneven or 

 " heterocercal " than that of the garpike, and thus it comes 

 nearer to the bony fishes. Its spinal column and skull are 

 also bony, and it indeed differs but in details from the 

 bony fishes. 



LiTBBATUBB. 



WUder. Qarpikes, old and young (Popular Science Monthly, 

 May and June, 1877); and notes on the North American Ganoids 

 (Proc. Amer. Assoc. Adv. Sc, 1875). 



Agassiz. Development of Lepidosteus. Pt. I. (Proc. Amer, 

 Acad. Arts and Sci., xiv. 1878.) 



Mark. Studies on Lepidosteus. Pt. I. (Bull. Mus. Comp. Zool., 

 XIX. 1890.) 



Balfour and Parlcer. On the Structure and Development of Lepi- 

 dosteus. (Phil. Trans. Roy. Soc, London, 1882.) 



With the writings of J. Muller, Hyrtl, KOUiker, Gegenbaur, LUt- 

 ken. Boas, Hertwig, Garman, etc. 



