PLATE L1V. 
Petromyzon ordine dentium unico. Bloch. Fisch. Deutschl. 3. 
p. 41. /. 88. f. 1. 2. 
Mustela. Plin. lib. 9. c. 19. 
Lampreda. Gem. ic. anim. p. 326. 
Le Petromyzon pricka. Bose. Hist. Nat. — Petite Lampvoie, or 
lamproie de riviere. Bujfon de Deterville, Sic. 
Lesser Lamprey. Penn. Brit. Zool. v. 3. p. 60. n. 2. 
The lesser Lamprey is specifically defined by the angulated struc- 
ture of the second dorsal fin. Bloch thinks it is to be distinguished 
from the rest of the Petromyzon genus by the teeth ; which, accord- 
ing to this writer, consist of a single series disposed in a circular man- 
ner within the mouth. Llis account is different from that of our 
countryman Mr. Pennant. Hie latter compares tire form of the 
mouth to that of the sea lamprey. “ On the upper part (he says) 
is a bifurcated tootli , on each side are three rows of very minute 
ones ; on the lower part are seven teeth, the exterior of which on 
each side is the largest.” 1 o reconcile those authors is no task of 
difficulty. Mr. Pennant has taken into consideration the detached 
teeth in different parts of the mouth, while Bloch regarded only those 
which are conspicuous in the upper and lower series, and even those 
he does not speak of with his accustomed accuracy. 
Since Dr. Bloch considers the disposition of those teeth as a speci- 
fical cntci ion of Petromyzon fluviatilis, it will not be thought improper 
to describe them minutely. In the anterior part of the mouth 
we observe a singular bony process, or tooth, of a size comparatively 
very large, which being curved and pointed at both extremities, r«- 
