Jordan and Evermann. Fishes of North America. 11 



a. Head 1% in length; iufraoral lamina with 7 cusps. CONCOLOR, 9. 



aa. Head 9 in length; infraoral lamina with 7 to 12 cusps. CASTANKUS, 10. 



9. ICHTHYOMYZON CONCOLOR, (Kirtland). 



(SILVERY LAMPREY.) 



Body considerably compressed; head broad, with large buccal disk, 

 which is moderately fringed; teeth strong and nearly uniform, the 2 

 supraoral teeth being similar to those on the rest of the disk ; lateral 

 teeth all simple ; iufraoral cusps coimivent, 7 in number, the middle ones 

 the longest; upper margin of dorsal scarcely depressed in front of the 

 vent; origin of dorsal nearly midway between the tip of snout and end 

 of tail ; 51 muscular impressions between gill openings and vent. Head 

 7|; depth 12. Color, silvery, bluish above, sometimes with bluish spots ; 

 a small dusky spot above each gill opening, usually conspicuous even in 

 the larva ; larva with small toothless contracted mouth, as in P. marinus. 

 It may be that this is the young of Petromyzon marinus. L. 12 inches. 

 Great Lakes and upper Mississippi Valley ; rather common ; ascending 

 small brooks in the spring, (concolor, uniformly colored.) 



Petromyzon argentcns, KIRTLAND, Bost. Jour. Nat. Hist., in, 1840, 342, with plate (name pre- 

 occupied), Big Miami River. 



Ammococles concolor, KIRTLAND, I. c., 473, with plate (larva), Mahoning River ; Scioto River. 

 ? Ammoccctes borealis, AGASSIZ, Lake Superior, 252, 1850, Michipicoten River. 

 ? Ammocottes fepyterus, ABBOTT, Proc. Ac. Nat. Sci. Phila., I860, 327 (larva), Ohio River. 

 Pftmmyzon bdellium, JORDAN, Cat. Fish. N. A., 4, 1885, after Kirtland. 

 Petromyzon concolor, JORDAN & FORDICE, Ann. N. Y. Ac. Sci., 1886, 282. 

 IchtJtyomyzon argenleus, JORDAN & GILBERT, Synopsis, 10, 1883. 



10. ICHTHYOMYZON CASTANEUS, Girard. 



Supraoral lamina tricuspid; some of the lateral teeth bicuspid; infra- 

 oral lamina with 7 to 12 cusps ; head 9 in length ; otherwise as in L concolor, 

 the color more yellowish. L. 12 inches. Mississippi Valley, scarce.* 

 (castaneuSj chestnut color. ) 



IdtOiyomyznn castancns, GIRARD, Pac. R. R. Surv.,381, 1858, Galena, Minnesota. 



L-ldJnjimiyzon hinulo, GIRARD, I. c., 382, Fort Smith, Arkansas. (Type, No. 980.) 



r>'tn-iin/r.<i cust'in>'>i*, JORDAN & GILBERT, Synopsis, 808, 1883, and JORDAN & FOBDICE, I. c., 281, 1806; 



Gf NTHER, Cat., vni, 507, 1870. 

 Idithyomyzon hirudo, GiiNTHER, Cat., VIII, 507, 1870. 



8. ENTOSPHENUS, Gill. 



Entosphenw, GILL, Proc. Ac. Nat. Sci. Phila., 1862, 331, (Iridenlatu?, name only); JORDAN & GIL- 

 BERT, Synopsis, 7, l8K^(tridenta(us) . 



Lampreys of large size, with the supraoral lamina forming a crescent- 

 shaped plate on which are 3 cusps, the middle one little smaller than 

 the others; anterior lingual tooth wedge-shaped, its edge almost straight 

 and finely pectinate; lips fringed; buccal disk moderate, its teeth com- 

 paratively few; dorsal fins separate. One species, a large anadromous 



* Recorded from Galena, Minn. (Girard); Mill Creek, Shawnee Co., Kans. (Cragiu); Fort 

 Smith, Ark. (Girard); Forlorn Hope, La. (Bean); Manitoba (Evermann). 



