THE DISTRIBUTION OF FRESHWATER OCRAYFISHES. 315 
fishes, some very curious points of approximation become 
manifest. The Salmonide, or fishes of the salmon and 
trout kind, a few of which are exclusively marine, many 
both marine and freshwater, while others are confined 
to fresh water, are distributed over the northern hemi- 
sphere, in a manner which recalls the distribution of 
the Potamobine crayfishes,* though they do not extend 
so far to the South in the new world, while they go a 
little further, namely, as far as Algeria, Northern Asia 
Minor, and Armenia, in the old world. With the excep- 
tion of the single genus Retropinna, which inhabits New 
Zealand, no true salmonoid fish occurs south of the 
equator; but, as Dr. Ginther has pointed out, two 
groups of freshwater fishes, the Haplochitonide and the 
Galaxide, which stand in somewhat the same relation to 
the Salmonide as the Parastacide do to the Potamobiide, 
take the place of the Salmonide in the fresh waters of 
New Zealand, Australia, and South America. There 
are two species of Haplochiton in Tierra del. Fuego; and 
of the closely allied genus Prototroctes, one species is 
found in South Australia, and one in New Zealand; of 
the Galaxide, the same species, Galaxias attennuatus, 
occurs in the streams of New Zealand, Tasmania, the 
Falkland Islands, and Peru. 
Thus, these fish avoid South Africa, as the crayfishes 
* According to Dr. Giinther their southern range is similarly limited by 
the Asiatic Highlands. But they abound in the rivers both of the old 
and new worlds which flow into the Arctic sea; and though those on 
