120 ZOOLOGY OF THE VOYAGE OF THE BEAGLE. 



Colour.— {In spirits.) Greenish-brown, with numerous conspicuous spots and small irreo-ular 

 transverse bars of black. Under a lens the spots appear to be made up of thickly crowded 

 black specks upon a dark brown ground : the bars result from some of the spots being con- 

 fluent. The belly appears to have been white. The rays of all the fins are dotted with dusky, 

 but the membranes transparent and colourless. 



The individual described above was taken by Mr. Darwin in a fresh-water 

 brook, in Hardy Peninsula, Tierra del Fuego. His collection, however, contains 

 four other specimens found in streamlets and creeks high up the river of Santa 

 Cruz in Patagonia, where they are said to have been numerous. Though these 

 last are slightly different, they are evidently referable to the same species : they 

 also vary a little from each other. Their peculiarities are as under : 



The largest measures 2 inches 8 lines in length, and has the following fin- 

 ray formula : 



D. 12; A. 16 ; C. 16, &c. ; P. 14 ; V. 7. 

 The next in size is 2 inches 6 lines, with the fin- ray formula thus : 



D. 11; A. 16; C. 16, &c. ; P. 13; V. 7. 

 These specimens agree in being both slenderer than the one from Tierra del 

 Fuego. The depth is eight and a half, if not nine times in the entire length : the 

 head rather more than one-sixth of the same. The colours are similar, except 

 that the spots are not quite so numerous, and of a more regular form, seldom 

 running together to form bars. 



It is to these specimens that Mr. Darwin's notes refer, respecting the colours 

 of this species in the recent state. As follows : " Pale greenish brown, with small 

 irregular transverse bars of black ; belly snow white." — D. 



The third of the Patagonian specimens is 2 in. 2 lin. long. Fin-ray formula— 



D. 10 ; A. 15 ; C. 16, &c. ; P. 14 ; V. 7. 

 The fourth is of the same length. 



D. 1 1 ; A. 15 ; C. 16, &c ; P. 13 ; V. 7. 



These last two specimens are exactly similar to each other in colours, but 

 differ from the former two in being almost immaculate, having only a few spots 

 on the upper part of the back. This brings them very close to the following 

 species, from which they are scarcely to be distinguished, except by their smaller 

 eyes. It should be observed further, that the fleshy part of the tail in these 

 specimens has the upper and under edges fringed with the short accessory rays 

 of the caudal, a character which is not so obvious in any of the others. 



