Table of Contents. vii 



PLATES. 

 I. Facing p. 14. Map of Potomac River, Great Falls to Little Falls. 

 II. Faciiio; p. 14. Hypentelium nigricans, showing position of fins. 

 III. Facing p. 85. Pipunculus industrius and P. vagabundus. 



The Committee on Publications declares that each paper of this volume 

 was distributed on the date indicated on its initial page. The index, 

 title page, and minutes of meetings for 1915 (pp. i-xiv, 185-189) were 

 issued on January 25, 1916. 



