10 CYCLOSTOMI : HYPEROAETIA. — III. 



Order III. HYPEKOAKTIA. 



Characters given above. One family only, (vnepaa, palate ; 

 apnos, complete.) 



Family III. PETROMYZONTIDuSl. (The Lampkeys.) 



Body eel-shaped, naked, compressed behind ; mouth subcircular, 

 armed with horny teeth, which rest on papillse ; 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 

 Ammocoetes 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 Am3ioc<etes, 3. 



66. Supraoral lamina contracted, of two or three teeth close together; discal 

 teeth numerous, in concentric series; buccal disk large (in adult, 

 very small in larva) Peteomtzos, i. 



3. AMMOCCETES Dumeril. (afifioi, sand ; koItt), 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. (Ammocoetes.) 



3. A. branchialis (L.). Mud Lamprey. Brqok 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 4f; myocommas 67, between gills and vent; an anal' papilla 

 present in spring. Color bluish black. L. 8. Cayuga L. ( ^Ieek) 

 to Minn, and Ky., ascending brooks in spring. {Eu.) fp • 

 Raf., not of Lacepfede.) (Lat., having gills.) v • i? > 



4. PETROMYZON (Artedi) Linnaeus, (nhpa, stone • 

 jtiufo), to suck.) ' 



a. Anterior lingual tooth divided in two by a median groove ; dorsal fi 



tinuous, with a broad notch. {Ichthyomyaon GiiSiri.) n con- 



4. P. castaneus (Girard). Supraoral lamina (maxillarv t 

 tricuspid; some lateral teeth bicuspid; infraoral lamina (manili^ 



