232 Field Museum of Natural History — Zoology, Vol. VII. 



Ichthyomyzon concolor (Kirtland). Silvery Lamprey. 



Head 6.5 to 8.3; depth 9.8 to 13.8. Body elongate, eel-shaped; 

 mouth a suctorial disc, anterior and slightly inferior and with mar- 

 ginal fringe; supraoral plate usually bicuspid, occasionally with i, 

 3 or 4 cusps; infraoral plate with 7 to 9 cusps, occasionally with 10 

 to 13; anterior lingual tooth with a median groove; diameter of eye 

 6 to 8 in head; muscular impressions between last gill opening and 

 vent 49 to 55; dorsal fin continuous with the caudal. 



Color silvery, bluish above, sometimes with bluish spots; a small 

 dusky spot above each gill opening. 



Length about 10 inches. 



This lamprey occurs in the Great Lake Region and the Upper 

 Mississippi Valley; it is parasitic on all larger fishes, but prefers fishes 

 without scales, as the catfishes, of the soft-scaled, as the suckers, to 

 the hard-scaled fishes, like the basses and perch. 



It ascends small brooks in the spring to spawn, after which it is 

 believed to die. The eggs deposited in nests on the bottom of the 

 streams soon hatch, and the small worm-like larva burrows in the 

 sand, where it remains from 3 to 5 years, when it emerges as a full 

 grown lamprey. Often found in the pound nets set at south end of 

 Lake Michigan. 



Lake Michigan, Whiting, Indiana; Lake Michigan, Edgemoor, 

 Indiana. 



Genus Lampetra Gray. 



Brook Lampreys. 



Supraoral plate, crescent-shaped, with a cusp at end, with occa- 

 sionally a small median cusp; anterial lingual tooth with median en- 

 larged denticli; dorsal fin with a sharp notch or entirely divided. 

 Small lampreys inhabiting brooks and small streams of Europe and 

 eastern North America. 



Lampetra wilder! (Gage). Brook Lamprey; Small Black Lamprey. 

 Head 7.9 to 8.7; depth 13 to 16. Body elongate, eel-shaped; 

 mouth a suctorial disc, anterior, and slightly inferior, and with mar- 

 ginal fringe of closely set tubercles; supraoral plate with cusp at each 

 end, separated by a distance nearly twice the width of base of a single 

 cusp; infraoral plate with 6 or 7 cusps, the extreme ones much larger 

 than the others ; 3 lateral cusps on each side of the mouth bicuspid, the 

 others simple; diameter of eye 5 to 7 in head; muscular impressions 



