758 FISHES — PETEOMYZONTID^. 



Desoriptloa. — Body stontiA, oiiiipre333d beTxiai ; hsitl broad, with large buooal disk 

 the edges of which are fringed but not oonspieously ; teeth pretty strong and nearly 

 uniform, the two mixiliary cusps being very similar to the other teeth ;' mandibulary 

 cusps seven in number, connivent, the middle ones the longest; color bluish, sides 

 silvery ; often mittled ; a small dusliy spot above each gill opening, usually conspic- 

 uous. Length about a foot. 



Habitat, Great Lake ragion and Mississippi and Ohio Valleys, mostly in deep water 

 but ascending small strsams 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 Erie 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 Erie, both external, feeding on the Perch, and internal, having 

 been devoured by the fish. Dr. Kirtland's original type was found 

 fastened to a Wall-eyed Pike (Slizostethium) . 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 a spot until 

 they have eaten through to the flesh, and deep ulcerous cavities occasion- 

 ally result from the sore" (Milner, Rept. U. S. Fish Comm., 1872-73, p. 

 74). According to Dr. C. C. Estes and others, this species likewise finds 

 " green pastures " on the naked skin of Polyodon. 



CLASS II. PISCES. THE TRUE FISHES. 



Excluding the Chimasras, 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 

 ray,-3 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, 



