FAMILY PETROMYZONIDE — PETROMYZON. 381 
THE BLUISH SEA LAMPREY. 
PETROMYZON NIGRICANS. 
PLATE LXXIX. FIG. 247. 
Petromyzon nigricans. Lxesvrur, Am. Phil. Soc. new series, Vol. 1, p. 395. 
The Bluish Lamprey, P. id. Storer, Report on the Fishes of Massachusetts, p. 196. 
Characteristics. Dorsals distinct, white. Mouth with incurved teeth, projecting from widened 
bases. Length five to seven inches. 
Description. Body cylindrical on its anterior third, compressed behind. Head oval, flat- 
tened on the top. Length of the head to the posterior angle of the eye, to the total length, 
less than one-seventh. The branchial orifices running obliquely backward and downward 
from the eyes. Mouth circular, half an inch in diameter, surrounded by a fleshy margin ; 
armed within with numerous incurved teeth or horny spines projecting from widened bases, 
resembling the spines with which the Raiw are armed. Three teeth in the throat; two 
higher up than the third, which is in front of and between the others. In the general ap- 
pearance of the tecth, there is great resemblance between those of this species and the pre- 
ceding. Eyes moderate. A spiracle on the top of the head, anterior to the eyes. The first 
dorsal fin commences back of the middle of the fish ; its posterior portion rounded ; its height 
to its length as 2 to 8. The distance between the dorsals is equal to half the length of the 
first dorsal. The second dorsal considerably higher than the first; before reaching the caudal 
fin, to which it is continued, it is depressed. Caudal fin a simple membrane, triangular at its 
termination, and uniting with the anal fin, which is very small. Anus small. 
Color. Upper part of the body of a deep blue color; beneath bluish white. Pupils black ; 
irides silvery. Between the eyes, on the top of the head, a small white spot. Dorsals white ; 
the second occasionally margined with bluish. 
Length 5°0-7°0. 
I am only acquainted with this species through the descriptions of Lesueur and Storer. 
It is found attached to mackerel, haddock and cod fishes. 
THE SMALL LAMPREY. 
PETROMYZON APPENDIX. 
PLATE LXIV. FIG. 211. 
Characteristics. Dorsals continuous, yellow. Anal fin with a thread-like appendix on its 
anterior portion. Length four to six inches. 
Description. Body cylindrical, compressed on its posterior half. Head rounded in front. 
Eyes large, prominent, and near the dorsal outline. ‘Temporal orifice tubular, central, and 
about two-tenths of an inch anterior to a line drawn across the eyes. Mouth beneath, circu- 
