tETROMYZONTID^. — III. 1 1 



ulary tooth) with 7 to 12 cusps. Color yellowish. L. 10. Miss. 

 Valley, Minn, to Kans. and La. (Ichth. hirudo Girard.) (Lat., 

 chestnut-colored.) 



5. P. concolor (Kirtland). Supraoral lamina bicuspid; teeth 

 on disk all simple, and placed in about 4 concentric series ; infra- 

 oral lamina with 7 cusps ; head 7^ ; with gills 4f ; 51 muscular im- 

 pressions between gills and vent. Color bluish silvery, sometimes 

 mottled ; a small bluish spot above each gill opening, — this found 

 even in the larva. L. 12. L. Erie to Mo. and N., a common para- 

 site on the Sturgeon and other large fishes. (P. argenteus Kirtland, 

 not of Bloch.) (Lat., uniformly colored.) 



aa. Anterior lingual tooth with a deep median groove, and extending in an 

 incurved point ; dorsal fin divided. (Petromyzon.) 



6. P. marinus L. Great Sea Lamprey. " Lampeb Eel." 

 Supraoral lamina bicuspid ; infraoral cusps 7 to 9 ; first row ol 

 lateral teeth on side of mouth bicuspid ; the others simple ; myo- 

 commas, 64 between gills and vent ; males in spring usually with 

 an elevated fleshy ridge before the dorsal. Color dark brown, 

 usually mottled with blackish. L. 3 feet. N. Atlantic, S. to Va., 

 ascending rivers to spawn, and permanently land-locked (var. uni- 

 color, Dekay) in the lakes of W. and N. N. Y. The larva is blind, 

 toothless, with a contracted mouth, in which the lower lip forms a 

 lobe distinct from the upper. The eyes appear before the mouth 

 is enlarged. (£m.) 



In the spring the Lamprey ascends small brooks for the purpose of de- 

 positing its spawn. They are then often found clinging to stones and clods 

 of earth. Later in the season they disappear, and are seldom seen except 

 when attached to some unlucky fish. They are rarely seen descending the 

 stream, and " it is thought by fishermen that they never return, but waste 

 away and die, clinging to rocks and stumps of trees for an indefinite period ; 

 a tragic feature in the scenery of the river bottoms worthy to be remembered 

 with Shakespeare's description of the sea floor." (Thoreau.) 



