SILVERY LAMPREY. 757 



Habiia. — This Lamprey is usually seen in the spring, when it ascends 

 small clear brooks, in large numbers for the purpose of depositing its 

 spawn. They are often found clinging to stones and clods of earth, in 

 which position, they are readily destroyed by the small boy. Later in the 

 season they disappear, probably returning to deeper water, and are sel- 

 dom caught except when attached to some unlucky fish. As they are 

 rarely seen on their way down stream, " 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.') 



They probably occur throughout Ohio, but are more abundant further 

 northwest. They have, of course, no economic value. 



GBNU8 2. SCOLECOSOMA. Girard. 



Scoleeoioma, Girakb, U. S. Pao. E. E. Snrv., x, 384, 1859. 

 Type, Ammocmtes concolor, Kiktland, which is the larval form of Petromyzon argenteus, 



KiRTLAJSD. 



Etymology, sTcolex, worm ; soma, body. 



Lampreys of rather email size, having the dorsal fin high and continuous, with only 

 a shallow emargination ; the teeth nearly equal over the large buccal diet, the maxillary 

 teeth two in number, pointed and set close together, without interspace and not form- 

 ing a crescent shaped plate ; mandibular plate with numerous olose-set pointed cusps, 

 which resemble distinct teeth. This genus differs from Pttromyzon in the continuous 

 dorsal, there being two distinct dorsal fins in the latter genus. Its known species in- 

 habit the Great Lake region and the Mississippi Valley. The group was originally in- 

 tended to include only those blind species (i. e. larvae) which had a single dorsal fin, 

 those larv86 with two dorsal fins being called by Girard Ammocoetes. The type of 

 Scalecosoma really seems to be a representative of a distinct genus, for which the name 

 is of course to be retained in spite of the erroneous views entertained as to its relations 

 by its author. 



2. ScoLECOSOMA ARGENTEUM (Kirtlaud) Jordan. 



Silvery JLamprey; Mud Eel. 



Petromyzon argenteus, Kirtland (1840), Boat. Journ. Nat. Hist., iii, 342. 

 loUhyomyzon argenteus, Jordan (1876), Man. Vert., first edition. 

 Ammocoetes argenteus, Jordan (1878) Man. Vert., second edition. 

 Ammocoetes concolor, Kirtland (1810), Bost. Journ. Nat. Hist., iii, 473 (larva). 

 Ichthyomyzon hirudo, Girard, (1859), U. S. Pao. E. E. Snrv., x, 342.— Qunthkr (1870), 

 . Cat. Fishes Brit. Mus., viii, 507. 



Ammocoetes hirudo, Jordon, Man. Vert., second edition, 350. 

 Ammocoetes aepypiera, Abbott (1860), Proc. Acad. Nat. Sci. Phila., 327 {larva). 



