72 CONTRIBUTIONS TO NORTH AMERICAN ICnTHYOLOGY IV. 



waters one has been described from the Saudwicli Islands. It is in view 

 of the probability of its occurrence as an occasional visitor on our West- 

 ern coasts that it is introduced. 



As already noticed, in Volume VI, page 172, of the Bulletin of the 

 Museum of Comparative Zoology, the species recently described by Dr. 

 Giinther, Trygon hrachyurus and Trygon reticulatus, belong to the genus 

 Potamofrygon, which includes the peculiar species of the family inhabit- 

 ing the rivers of South America. 



