10 CYCLOSTOMI: HYPEROARTIA, — III. 
Orper Il HYPEROARTIA. 
Characters given above. One family only. (imepga, palate ; 
Gprios, complete.) 
Famity III. PETROMYZONTIDA), (Tue Lampreys.) 
‘Body eel-shaped, naked, compressed behind ; mouth subcircular, 
armed with horny teeth, which rest on papille; gill openings 7, 
arranged in a row along the side of the “chest”; lips present, 
fringed ; nostril on top of head, just in front of eyes; dorsal fin 
more or less notched; intestine with a spiral valve; eggs small. 
The lampreys undergo a metamorphosis, the larva of all species 
being toothless and having the eyes rudimentary. The name 
Ammoccetes was formerly applied to the larval forms; originally, 
however, to that of A. branchialis. Genera 3 or 4, species about 
15, chiefly of the fresh waters of temperate regions. ‘They attach 
themselves to fishes, and feed by scraping off the flesh with their 
rasp-like teeth. 
a. Second dorsal joined to the caudal. 
b. Supraroral lamina (‘‘ maxillary tooth’) expanded laterally, forming a 
crescent-shaped plate, with a cusp at each end, and sometimes a median 
cusp; anterior lingual teeth serrate... . . . . . AMMOC@TES, 3. 
66. Supraoral lamina contracted, of two or three teeth close together; discal 
teeth numerous, in concentric series; buccal disk large (in adult, 
very smallin larva). . . + » « + © « + + PETROMYZON, 4. 
3. AMMOCCETES Duméril. (dypos, sand; xotry, bed.) 
a. Supraoral lamina with a very small median cusp or none; edge of anterior 
lingual tooth small, crescent-shaped, dentate, the median denticle en- 
larged; buccal disk small, with few teeth. (AMMOC@TEs.) 
3. A. branchialis (L.). Mup Lamprrey. Broox Lamprey. 
Dorsal continuous, deeply notched, both parts high; about 3 
bicuspid teeth on each side of buccal disk; the other teeth sim- 
ple; infraoral plate with 5 to 9 blunt subequal cusps; head with 
gills 48; myocommas 67, between gills and vent; an anal papilla 
present in spring. Color bluish black. L. 8. Cayuga L. (Meek) 
to Minn. and Ky., ascending brooks in spring. (Eu.) (P. niger, 
Raf., not of Lacepéde.) (Lat., having gills.) 
4, PETROMYZON (Artedi) Linnzus. (zérpa, stone; 
pio, to suck.) 
a, Anterior lingual tooth divided in two by a median groove; dorsal fin con- 
tinuous, with a broad notch. (Jchthyomyzon Girard.) 
4. P. castaneus (Girard). Supraoral lamina (maxillary tooth) 
tricuspid ; some lateral teeth bicuspid ; infraoral lamina (mandib- 
