eigenmann: fresh water fishes. 273 



will be furnished with a clue to a problem that has so often been dis- 

 cussed on insufficient data." 



The species of this genus recorded from Patagonia have received elab- 

 orate consideration from Smitt. He found that the young differs greatly 

 from the adult and that three stages may be distinguished, "alevins," less 

 than 45 mm., "fretins," about 50 mm., and adult, over 60 mm. Species 

 based on these larval stages are scarcely recognizable. The difference 

 between the alevins and the fretins of the same species is greater than the 

 differences between two adult species. The only character distinguishing 

 the species in all ages is the length of the lower jaw in relation to the 

 distance of the dorsal from the tip of the snout. 



He distinguishes the two species recognized by him as follows : 



a. Head 1 8.8-20. i per cent, of the length ; distance of origin of dorsal from tip of snout 72-74.8 

 per cent, of the length ; distance of origin of ventrals from tip of snout 48.5-52.1 per cent, 

 of the length; pectoral 1 1 ; A. 13-15; lower jaw 9.3-10.2 per cent, of the length from tip 

 of snout to dorsal. viaadatus. 



aa. Head 22.4-26.6 per cent, of the length ; distance of origin of dorsal from tip of snout 53.8- 

 56.6 per cent, of the length; P. 13-15 ; A. 9-12; lower jaw 12. 9-16.3 per cent, of the 

 distance from tip of snout to dorsal. alpimis. 



The color of the alevins of both species is uniform yellowish or gray. 

 In the alevins of macitlatns a series of pigment cells follows the dorsal 

 border posteriorly; another follows the ventral border and alimentary 

 canal ; another series along the lateral line, another along the upper mar- 

 gin of the notochord ; a black bar at base of pectoral ; a black spot at 

 upper angle of preopercle and others on snout and top of head. 



During the fretin stage the color of the two species is alike and 

 remains so till the species has reached a length of about 8.5 cm. 



More recently Regan, Proc. Zool. Soc. London, 1905, II (April 1906), 

 considered the fretins of Smitt as a distinct species, gracillimiis of Canes- 

 trini. Smitt's alpimis he considers in part attemiatiis, in part macitlatns 

 and in part platci. 



Regan defines six American species of which alpinns is confined to the 

 alpine lakes of Hardy Peninsula, Tierra del Fuego, and sniittii to the 

 Falkland Islands. The remaining four are distinguished as follows : 



a. Six or seven branchiostegals ; caudal emarginate ; origin of anal opposite or slightly posterior 

 to that of the dorsal. 

 b. Origin of ventral equidistant from tip of snout and base of caudal or nearer the former. 



