3. PETROMYZONTID^ — ICHTHYOMYZON. 9 



5.— AITIITIOCaiTES Dum^ril, 1817. 



Brook Lampreys. 



(Diuu<^ril — Cuvier, Ecgne Animal : type rctrowijzon ira.ivldaHn L. =^tlio larval form of 

 I'etromyzon pJaueri Blocli.) 



Lampreys of small size, with tlie dorsal fin coiitimious, sometimes 

 emarginate, but never divided into two fins, the posterior portion con- 

 tinuous with the low anal fin around tlie tail ; maxillary tooth single, 

 hroad, forming a crescentic plate, with a larg(^ bluntish (;usp at each 

 end, and sometimes a small median cusp; lateral teeth very few ; tongue 

 with two broad transverse i^lates, each with a median cusp; species fcAV ; 

 our single species is scarcely distinguishable from the common "Pride" 

 or "Small Lamprey" of Europe, Ammocoetes hranchiaUs. [ujj.ijj)^^ sand; 



7.11 irri^ to lie.) 



8. A. nig'er (Raf. ) Jor. — Small Illack Lamprey. 



Head moderate, nearly as long as the "chest"; the mouth compara- 

 tively small; lips with a conspicuous fringe of papilhie; dorsal fin high, 

 considerably dei)ressed in front of the vent, but not divided into two 

 fins; the posterior lobe highest; anal fin evident ; anal tube conspicu- 

 ous in the spring ; eyes moderate ; maxillary tooth with its cusps large, 

 triangular, well separated; a small i)oiuted median cusp usually present 

 in the adult ;■ in younger specimens the median cusp is obsolete, and in 

 hall^grown specimens the tooth forms a curved plate without distinct 

 cusi)s ; nmndibular i)late curved, with eight to ten well developed sub- 

 equal tooth-like lobes; inside of it is a plate bearing three teeth ; lingual 

 teeth traus\'erse, trifid ; a plate on each side of the buccal orifice ; the 

 remaining 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 with the European Aimno- 

 coetcs hranchiaUn. 



{Vciromyzon n'ujrum Eaf. Icli. Oh. 84; Jordan, 349.) 



6.— ICIITIIYOMYZOIV Girard, 1859. 

 Silvery Lampreys. 



(Girard, Pao. R. R. Surv. x, :!.S1 : tyix; I'dromyzoit aryintcnn Kirtland.) 



Lampreys of rather small size, luuing the dorsal fin high and con- 

 tinuous, with only a shallou' emargination ; the teeth nearly ('([ual over 



