72 CONTRIBUTIONS TO NORTH AMERICAN ICHTHYOLOGY IV. 
waters one lias been described from the Sandwicb Islands. It is in view 
of the probability of its occurrence as an occasional visitor on onr West- 
ern coasts that it is introduced. 
As already noticed, in Volume VI, page 172, of the Bulletin of the 
Mnseuin of Comparative Zoology, the species recently described by Dr. 
Giintiier, Trygon hracJiyiiriis and Trygon reticuJatus, belong to the genus 
Potamotrygon, whicli includes the peculiar species of the family inhabit- 
iug the rivers of South America. 
