Petromyzon. 
1 Le sh Pi 5 to and a half inches. 
This species is allied to the present gehus by the 
form of the body and by the seven lateral branchial 
apertures, but it differs by its long anal fin and by the . 
juuction of the two dorsals which are separate in oth- 
Fe LA vpaciass It approaches the P. argenteus, B1 XIL- 
e inhabits bisky running waters, attaching itself 
4o rocks which receive cascades; whence it immediate- 
h, £ ly recedes when approached. As its vision is very 
good, it is necessary torbe quick in attempting to sieze 
> * if, im order to secure it. Of seven individuals 
e obtaiued, but one was a male; t the others 
ee ntained numerous eggs. "The water over the rocks 
AT which we observed them, was from 2 inches to 7 
me 1 Je £ormed hy thérapia cnvrrent and 
2 d the rays of the sun. We designated 
his cave by the name of the proprietor Mr. Wilkin- 
% ; it consists of a superposition of sand stone, on 
+ Gite and diabase, and wiil receive a more particu- 
‘lar description in an account of an excursion made in 
April 4820 by Dr. Troost and myself to the Lamotte 
“mine in Missouri. My specific name is that of La- 
: motte, one of the companions of Renault, who disco- 
+ vered this mine in 1720 when the French possessed 
that country. # : 
» The figure represents the mmtekit size. The Disk 
is that of an Lu nn of the pe teeih. 
EF 41:#: 
dé L7 
2 M [2 4 # 
# Li 
; + e 12 
LA 
+ 
4 
