282 North American Species of Petromyzontidm. 



than in P. concolor. It is probable that P. concolor and P. cas- 



taneus are distinct species, distinguished chiefly by the number 

 of supraoral cusps. 



3 PETROMYZON CONCOLOR. 



Petromyzon argenteus Kirtland, Boston Journal Nat. Hist.. 1840, 342, with 



plate (Big Miami R.). Gray, Cat. Ckondr. Fish. 1851. 139 (copied). 



Jordan & Gilbert, Synopsis Fish. N. A., 1883, 867 (not of Bloch). 

 Ichthyomyzon argenteus Cope, Proc. Ac. Nat. Sci. Phila., 1864. 276 (Michi. 



gan) ; Nelson, Bull. Ills. Mus. Nat. Hist., I, 52, 1876. Jordan, Man. 



Yert., 1880, 343. Jordan & Gilbert, Synopsis Fish N. A., 10, 1882. 

 Ammocaites argenteus Jordan, Man. Yert., Ed. I, 1876, 349; Jordan, Ann. 



N. Y. Acad. Sci., 1877, 120 (Lake Erie, White R., Ohio R ). 

 Scolecosoma argerdeum. Jordan, Zool. Ohio, IY, 1882, 757. 

 Ammocoetes concolor Kirtland, Bost. Journ. Nat. Hist., 1840, 473, wilb plate 



(larva ; Mahoning and Scioto Rivers). Gray, Cat. Chondr. Fish, 



Brit. Mus., 1851, 146 (copied). 

 Petromyzon concolor Jordan, Cat. Fish. N. A., 1885, 185. 

 ? Ammocoetes borealis Agassiz, Lake Superior, 1850. 252 (Michipicoten. Lake 



Superior). [Description not diagnostic ; may be young of P. marinus 



or of A. branchialis.] 

 ? Ammocoetes wpyplerus Abbott, Proc. Ac. Nat. Sci. Phila . 1860, 327. (Ohio 



River). [Description inadequate and perhaps inaccurate ; may be young 



of A. branchialis.~\ 

 Petromyzon bdellium Jordan, Cat. Fish N. A., 4, 1885 (substitute for P. argen- 

 teus, Kirtland, preoccupied). 



Habitat. — Great Lakes and Ohio and Mississippi Valleys, not 

 rare. 



The specimens examined by us are from the Ohio River at 

 New Albany, from Ohio, from White River, Mississippi River, 

 and from Lakes Erie and Michigan. 



This species is a common parasite of the sturgeon and other 

 large fishes. 



The specific name, "argenteus" by which the species has 

 been usually known, is preoccupied, for which reason Dr. Jor- 

 dan has recently proposed the new name of P. bdellium. A study 

 of the changes undergone by the larvae of P. war mus has con- 

 vinced him that the description of Ammocoetes concolor would 

 apply to the larvae of this species, the small size of the mouth 

 being one of the characters of larval forms. This view is ren- 

 dered more probable because of the presence in concolor of the 

 dark dots above the gill-openings which are seen in the adult 



