PETROMYZONTID^. CXVI. 349 



2. P. nigricans, L. LARGE BLACK LAMPREY. Head 



very large, longer than the "chest," 6^- in length; depth 

 about 13; body little compressed; dorsal fins rather low, 

 distinctly separated; eyes and mouth very large ; a 

 depression between eyes and snout; a single bicuspid 

 tooth in front of oesophagus; mandibulary plate curved, 

 with about eight pointed teeth; rest of mouth covered 

 with rather large teeth disposed in oblique cross-rows, 

 five or more in each row; lips fringed; L. 12. Lakes 

 and streams, Cayuga L., N. Y. (Wilder), and E.; prop- 

 erly a marine species. Also in Europe. (P. nigricans, 

 LeS., the American form.) (Several other Lampreys 

 have been described from our Eastern streams and coast, 

 but they are very doubtful.) 



2. ICHTHYOMYZON, Girard. LAMPERNS. 



1. /. argenfeum, (Kirt.) Gir. SILVERY LAMPREY. 

 Head quite small, shorter than " chest," about 10 in 

 length; depth nearly the same, in adult; body stout, 

 compressed; dorsal fin very high, with a shallow depres- 

 sion; eyes distinct in adult, concealed in young; mouth 

 small, with inconspicuous teeth; color ashy silvery, with 

 numerous small black dots; larger ones above the gill 

 openings; L. 12. Great Lakes and Ohio Valley, E. to 

 N. Y., frequent. (Ammoccetes concolor, Kirt., A. mpyp- 

 tera, Abbott.) 



3. AMMOC(ETES. DUMERIL LAMPERXS. 



1. A. niger, (Raf.) Jor. SMALL BLACK LAMPREY. 

 Head moderate, longer than " chest," 8 in total length ; 

 depth 14; body scarcely compressed except behind; 

 dorsal fins rather high, slightly connected; eyes large; 

 mouth rather small, one tooth with two cusps well apart 



