NO. 1528. 



A NEW FO>SSIL STICKLEBACK FISH— HAY 



273 



The fourth (Cat. No. 5389, U.S. N.M.) furnishes the body behind the 

 fronts of the dorsal and anal tins (tig. 3). Only S soft rays appear in 

 the dorsal and anal tins; but evidently at least one in each is missing. 



The slenderness of the body (depth in the length 5 times) differen- 

 tiates this tish from all the others except G. hisplnosus^ in which the 

 depth is 5.5. In all the others the depth does not go above 4 times in 

 the length. From the species G. h/sphwsus and its su])species cnvicrl 

 our fossil differs in the tin formula, that of G. splnosus being D. II, I, 

 12: A. I, 8. 



It is evident that the Lahontan fishes are most closely i-elated to the 

 typical form of G.willl(tnm>ni.,\\\Q, species now living within a few hun- 

 dred miles of the Lahontan beds. The fin formula of this species 

 differs only in having 8 soft anal rays. However, the body of the fossil 

 form is slenderer, the second dorsal spine is longer, entering the dis- 

 tance from the snout to the pupil once, instead of 1.5 to 2 times. The 

 first dorsal spine of the fossil appears to be much shorter than in the 

 living species considered. The ventral spines seem to be longer than 



Fig. S.— I'dSTKRlol; l'(.l;THiN 



El'TOSOJirS. xU. 



in G. irilliamsoni ^ and the ventral plates are considerably longer than 

 the snout and the or])it taken together; the snout and orbit l)eing 7 nnn. 

 long, the plates llnmi. 



From G. wilUavisoni laierocephalus the fossil form is distingnished 

 1)3^ several characters besides the slenderer body. There are more 

 raj^s in the anal tin and the ventral plates are longer. 



In the typical form of G. wlUiamsoni it is only in occasional indi- 

 viduals that the lateral armor is found, and in these only 2 or 3 plates 

 appear on each side. In micy'ocephalusihQVQ are usual h" 5 or 6 plates; 

 but there may be as many as 26. On the other hand, individuals are 

 sometimes found that are wholly devoid of lateral armor. 



The presence of this fossil stickleback in the Lahontan beds, related 

 as it is to <r. uun!am>ion!^ appears to indicate an age not older than 

 (Quaternary, and that the beds were deposited in fresh rather than in 

 salt or brackish water. 



Excepting a specimen supposed to belong to G. hispino-v/s, found in 

 the Pleistocene of Canada by Sir William Dawson, no fossil stickle- 

 back has hitherto l)een reported. 

 Froc. N. M. vol. xxxii— 07 18 



