GAR-PIKES, OLD AND YOUNG. 



187 



sisted in the existence of two tails, an upper and a lower. These are 

 shown in Fig. 8, JB. 



The formation of these two tails, and their significance, will be 

 considered further on ; for the present, we are concerned with tlioir 

 Structure, their relative position, and their uses. Tlie lower tail was 



Fig. 8. Four Figures op the Tails op Lepidosteus at Different Stages. 

 .4, from a specimen t wen ly-twomillimetiYS or seveii-eip;hths inch Idiip;, enlarged four diameters. 

 The ventral fin (Fe) is just appearing. The median fin is being absorbed between thefourspots 

 referred to in Fig. 9. The lip of the tail is inclined upward, and the infra-caudal lobe is 

 larger. In B the primordial fin lias almost disappeared ; the dorsal (/>) and the anal (A) fins 

 are quite large. The infra-caudal lobe is nearly aslont' as the tip of the original tail, which has 

 been reduced to a slender vibratile filament. This specimen is forty-four mi'limetres or one 

 and three-foiiitlis inch lonsr, and the tail is enlarged two ciameterf?. C shows the tail of a 

 specimen three hundred millimetres or nearly twelve inches long, of natural size. The fila- 

 ment is still furlher reduced, nnd tbe ravs of the infra caudal lobe form the end ot the tail In 

 I) the fail is that of an adult, one-half natural diametei-. The filament, the oiisrinal end nf the 

 body, has wholly disappeared, and the infra-caud.nl lobe forms the fail. But dissection shows 

 the spinal axis extending along the dorsal border to a point corresponding with the previous 

 attachment of the filamenr. (Further description and discussion of these changes, with refer- 

 ences to author.^, may be found in a paper by the author, entitled "Notes on the North Ameri- 

 can Ganoids." "Proceedings of the American Association for the Advancement of Science," 

 1875, pp. 151-193.) 



evidently the caudal fin. It had several rays, and a rounded hinder 

 border. But it was smaller in proportion than in the adult gar, and 

 the middle rays were directed obliquely downward, instead of hori- 

 zontally backward. 



The upper tail is best described as a single fleshy filament, flat- 



