3. PETROMYZONTID^ ICHTHYOMYZON. 
9 
5.— AMxTIOCiETES Dum^ril, 1817. 
Brooh Lampreys. 
(Dum^ril— Cuvier, Rogue Animal : type rctromxjzon bra.icliiaUs L. =tlie larval form of 
Petromyzon plancri Bloch.) 
Lampreys of small size, with the dorsal tiii continuous, sometimes 
emarginate, hut never divided into two tins, the posterior portion cou- 
tiuuons with the low anal fin around the tail ) maxillary tooth single, 
hroad, forming a crescentic plate, with a large bluntish cusp at each 
end, and sometimes a small median cusp ; lateral teeth very few ; tongue 
with two broad transverse plates, each with a median cusp ; species few ; 
our single species is scarcely distinguishable from the common “Pride"’ 
or “Small Lamprey” of Europe, Ammoccctes brauchiaUs. {d/jyio-^ sand; 
xotzTjj to lie.) * 
8. A. isiger (Raf.) Jor. — Small Blade Lamprey. 
Head moderate, nearly as long as the “chest”; the mouth compara- 
tively small; lips with a conspicuous fringe of papilla; dorsal tin high, 
considerably depressed in front of the vent, but not divided into two 
fins ; the posterior lobe highest ; anal tin evident ; anal tube conspicu- 
ous in the spring ; eyes moderate ; maxillary tooth with its cusps large, 
triangular, well separated; a small i)ointed median cusp usually present 
in the adult; iii younger specimens the median cusp is obsolete, and in 
half-grown specimens the tooth forms a curved plate Avithout distinct 
cusps; mandibular plate ciu-ved, with eight to tea Avell deA’eloped sub- 
e(iual tooth-like lobes; inside of it is a plate bearing three teeth; lingual 
teeth transverse, trilid ; a plate on each side of the buccal orilice ; the 
remaming teeth inconspicuous. Bluish black above; silvery below. Size 
rather small. L. G to 10. 
A small species ascending Western streams in the spring in great 
numbers to deposit its spawn. Great Lakes, Ohio Valley, and Upper 
Mississippi Eegion. It is perhaps identical Avith the Eiu’opean Ammo- 
coetes branchialis. 
(^Petromyzon nUjriim'RA. Icli. Oh. 84; Jordan, 349.) 
6.— ICIITIIYOMYZO^ Girard, 1859. 
Silvery Lampreys. 
(Girard, Pac. R. R. Surv. x, 381 : type Petromyzon argentens Kirtland.) 
Lampreys of rather small size, haA'ing the dorsal fin high and con- 
tinuous, Avith only a shallow emarginatiou ; the teeth nearly equal over 
