758 FISHES—PETROMYZONTIDA. 
Description —Body stoutish, compressed behind; head broad, with large buccal disk 
the edges of which are fringed but not conspicously ; teeth pretty strong and nearly 
uniform, the two maxillary cusps being very similar to the other teeth ; mandibulary 
cusps seven in number, connivent, the middle ones the longest; color bluish, sides 
silvery ; often mottled; a smali dusky spot above each gill opening, usually conspic- 
uous. Leigth about a foot. 
Habitat, Great Lake region and Mississippi and Ohio Valleys, mostly in deep water 
but ascending small streams to spawn in the spring. 
Diagnosis.—The presence of two teeth close together, and similar to 
the other teeth, in the mouth in front of the opening of the gullet will 
distinguish this Lamprey from the other species found in Ohio. This 
species is larger and paler colored. 
Habits.—This Lamprey is rather common, both in Lake Hrie and in 
the Ohio River. It is not often found in small streams, excepting in 
the spawning season. I have obtained several specimens, with Perch 
from Lake Hrie, both external, feeding on the Perch, and ¢nternal, having 
been devoured by the fish. Dr. Kirtland’s original type was found — 
fastened toa Wall-eyed Pike (Stezostethium). Probably all of our larger 
fishes sometimes are victims to its voracity. The species seems to reach 
nearly its full size before dropping its larval peculiarities, as blind and 
toothless specimens of six or eight inches in length are occasionally 
taken. 
According to Professor Milner, this Lamprey frequently is parasitic on 
the Lake Sturgeon, producing circular scars or raw sores. “It is proba- 
ble that their natural food is the slime or mucus exuded in abundance 
from the pores, but they frequently retain their hold upon aspot until 
they have eaten through to the flesh, and deep ulcerous cavities occasion- 
ally result from the sore” (Milner, Rept. U. 8. Fish Comm., 1872-73, p. 
74). According to Dr. C. C. Estes and others, this species likewise finds 
“‘sreen pastures ” on the naked skin of Polyodon. 
CLASS Il. PISCES. THE TRUE FISHES, 
Excluding the Chimeras, Skates, Sharks, Lampreys, Lancelets and 
their allies, fish-like vertebrates, which are not fishes in a strict zoologi- 
cal sense, a fish may be defined as follows: 
A fish is a cold blooded vertebrate, adapted for life in the water, having 
the limbs developed as fins, the dactyls being represented by cartilaginous 
rays connected by membrane (rarely obsolete); exo-skeleton, if present, 
of scales, spines, or bony plates; one or more fins on the median line of 
the body composed of rays connected by membrane; skull developed, 
