204 NORTH AMERICAN 



same latitude they are likely to give the most useful result. We have, 

 therefore, not counting the unrecognized species : — 



Peculiar to the Atlantic Region 32 



Peculiar to the Lake Region 33 



Peculiar to the Pacific Region oO 



Common to the Atlantic and Lake Regions only 24 



Common to the Lake and Pacific Regions only 



Common to the Atlantic, Lake, and Pacific Regions. . . o 



A few species peculiar to the Gulf, Rocky Mts., or Arizona faunas 

 are omitted, and if included would not tend to render the table more 

 significant. It should be mentioned, however, that there are three 

 species peculiar to the Lakes and Rocky Mts. only. It is also to be 

 observed that the Rocky Mts. constitute an almost insuperable barrier 

 to the intercommunication of the various species, only five being 

 common to the two slopes. 



ERRATA. 



Page 16, 1st line after description, for "Penington" read "Pennington." 

 " 29, 11th line from top, for "several" read "sexual." 

 " 47, 1st line from top, for " Firsh" read " Fish." 



" 38 and p. 63, for " eoiifusus" read "deductor," corifusus is pre- 

 occupied (Sahib. En. Col. brach. Fenn. 1876, p. 58). 



