400 



SILVER LAMPREY. 



Petromyzon argenteus, 



Block ; PI. 78, 3, which Cuvier pronounces 

 the figure of a young example of his F. 

 fluviatilis; which also he does not distin- 

 guish frona the Lampern. I believe them 

 to be different species, and that Bloch 

 represents the Silver Lamprey, which ia 

 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 Lampern, 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 aperture 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 



