10 CYCLOSTOMI: HYPEROARTIA. — III. 
OrpeErR II HYPEROARTIA. 
Characters given above. One family only. (timep@a, palate ; 
aptios, complete.) 
Famity Ill. PHTROMYZONTIDA. (THE LAmpReEys.) 
Body eel-shaped, naked, compressed behind ; mouth subcircular, 
armed with horny teeth, which rest on papilla; 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 
Ammoceetes 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. 
6. 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. . . . . . . AMMOCCTES, 3. 
bb. Supraoral lamina contracted, of two or three teeth close together; discal 
teeth numerous, in concentric series; buccal disk large (in adult, 
very small in Jarva).. 4) ise.) &P eS) sy « 4 SPET ROME eons: 
3. AMMOCCSTES Dumeéril. (dppos, sand; koirn, 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. (AMMOCGTEs.) 
3. A. branchialis (L.). Mup Lamprey. Brook 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 42; 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. (/u.) (P. niger, 
Raf., not of Lacepede.) (Lat., having gills.) 
4. PETROMYZON (Artedi) Linneus. (zérpa, stone; 
pu¢w, 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- 
