PETROMYZONTID^. — CXVI. 349 



2. P. nigricans, L. Laege Black Lamprey. Head 



very large, longer than the "chest," G^ 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 I^ampreys 

 have been described from our Eastern streams and coast, 

 but they are very doubtful.) 



2. ICHTHYOMYZON, Girard. Lampeens. 



1. /. argenteum, (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. (A^nniocoetes concolo)\ Kirt., A. cepyp- 

 tera^ Abbott.) 



3. AMMOCCETES. Dumeril Lamperns. 



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 



