Marsipohranchs of the Order II yperoartii. 199 



8. 720 mm. Coruna. Mons. V. L. Seoane. 



9. 800 mm. Lisbon, Rev. R. T. Lowe. 

 10. 170 mm. Mediterranean. 



IL 210 mm. W. Africa. J. C. Salmon, Esq. 



12. 180 mm. Nova Scotia. M. Jones, Esq. 



13, 14. 620-640 mm. New York. 



15. 530 mm. Merrimack R. 



16. 270 mm. Muscatine, Iowa. Field Mus. 



17. 170 mm. Val-de-Grace, U.S.A. Dr. F. Day. 



Specimen no. 11 has the supraoral cusps small and close 

 together and the iiifraoral cusps weak, as described for 

 Bathymyzon bairdii. 



4. ICHTHYOMYZON. 



Ichthjomyzon, Girard, Pac. R. R. Surv. x. p. 381 (1858). 



Disc covered with radially arranged teeth. A single 

 narrow bicuspid or tricuspid supraoral lamina ; infraoial 

 lamina cuspidate. Anterior lingual lamina with a single 

 transverse denticulated ridge. Dorsal fins united. 



Eastern North America. 



1. Ichthyomyzon bdellium. 



Petromyzon arqenteus (non Bloch), Kirtland, Bost. Journ. N. H. iii. 



1840, p. 342; pi. iv. fig. 3. 

 Petromyzon bdellium, Jord. Cat. Fish. N. Am. p. 4 (1885). 

 Ichthyomyzon concolor, Jord. & Everm. Bull. U.S. Nat. Mus. xlvii. 



1896, p. 11 *. 



Supraoral lamina bicuspid ; all the labial teeth unicuspid ; 

 infraoral lamina with 7 cusps. 



Great Lakes and Upper Mississippi. 



1. 240 mm. Louisville, Kentucky. Smithsonian Inst. 



2. Ichthyomyzon castaneits. 



Ichthyomyzon castaneiis, Girard, Pac. R. R. Surv. x. p. 381 (1858) ; 



Gunth. Cat. Fish. viii. p. 507 (1870) ; Jord. & Everm. Bull. U.S. 



Nat. Mus. xlvii. 1896, p. 11. 

 Ichthyomyzon hirudo, Girard, t. c, p. 382 ; Giinth. /. e, 



Supraoral lamina tricuspid; some of the lateral labial 

 teeth bicuspid ; infraoral lamina with 7 to 12 cusps. 

 Mississippi. 



• I cannot see that the larva described by Kirtland as Ajnmocaetcs 

 concolor differs in any way from that of Lampetra pluneri. 



