400 
SILVER LAMPREY. 
Petromyzon argenteus, Bloch; PI. 78, 3, which Cuvier pronounces 
the figure of a young example of his F. 
flmiatilis; which also he does not distin- 
guish from the Lampcrn. I believe thorn 
to be different species, and that Bloch 
represents the Silver Lamprey, which is 
a fish not generally recognised by natu- 
ralists; although Sir William Jardine 
appears to refer to it when he describes 
what he had observed of the actions of 
the Lamperu, as already quoted, and of 
another which he considered to be distinct 
from it. 
The Silver Lamprey is always of less size than the ordinary 
dimensions of the Lampern, and proportionally more slender; 
the form of the head different, in a more decided approach to 
a lip when viewed from above; the apertui’e on the head a 
little in front of a line between the eyes; dorsal fins only a 
little removed from each other, and the second joined by an 
evident continuation to the tail; the line of the branchial 
openings less depressed than in the Lampern in proceeding 
backward; being in a direct course with the line of the body. 
A line of pores on each side along a portion of the under 
surface, as represented in this figure. In this latter example 
there appears a process which perhaps appears only at the time 
