M. Valenciennes on Fishes and Reptiles. 167 
I am not acquainted with a genus of fishes which can be 
given as a marine form. Thus the Rays, an extensive sea 
family, inhabit the fresh waters of America; a Pastenague (a 
genus of the Ray tribe) is found in the Rio-del-Magdalena, at 
a height to which the water of the sea neyer reaches ; it is 
fished for in the neighbouring ponds. 
The Pleuronectes (Limandia and Soles) ascend rivers, the 
Loire, for example, even in its tributaries, so that they can 
be obtained for food at Roanne. Thus you see that Pleuro- 
nectes flesus would have a shorter course in returning to the 
sea by taking the Rhone as its conveyance to the Mediter- 
ranean. Ihave caught Limandia in the Seine at the Isle of 
St Denis, near Paris. The sole ascends the Rhine as far as 
Neuwied and Coblentz, where it is obtained for the table as 
at a sea-port. 
The Twaite Shads (Clupea alosa, L.) ascend periodically 
from the sea into fresh waters, and in the Seine they are 
found as far up as Provins. Some kinds take up their abode 
in the lake of Garda, and never leave the fresh waters; this 
is the case with the Agone of the Italians, which likewise 
lives in the Mediterranean. Eels when full grown pass from 
the fresh water into the sea, and again ascend when they 
have bred; the contrary takes place with the Aloses and Sal- 
mon. The lake of Biserte and others lying along the coast 
of Africa as far as Tunis are full of Spari and Scizne, &c., 
marine fishes, and of which large shoals live in both kinds of 
water. Mullets do the same in our basins of Arcachon. 
These seem to me a sufficient number of examples. The Mcl- 
lusca in this respect, are as well known to you as they are 
tome. In Sweden and Norway, Nilson found our Anodontes 
on the shores of the sea, where there was no fresh water; and 
the curious experiments of M. Macculloch, which I shall re- 
peat in another form if ever I have an opportunity, have like- 
wise been made on the Mollusca, All animals with a bran- 
chial respiration, always find enough of oxygen in the water 
for breathing, although the two kinds of water are not charged 
with the same quantity of air.* 
* From Annales des Sciences Naturelles, tom. xvi. p. 110. 
