No. 4-] AMPULLAE OF THE SELACHII. 177 



In conclusion I wish to express my appreciation of the help 

 received from Dr. Howard Ayers and of the generous resources 

 afforded me at the Williams College room in the Woods Roll 

 Laboratories. A considerable portion of this investigation has 

 been carried on at Harvard University and in the Williams 

 College laboratories. I am especially indebted to Prof. E. L. 

 Mark for his direction of my work during the year at Harvard; 

 and to Dr. James I. Peck of Williams College for assistance in 

 preparing my work for publication. The final copies of the 

 drawings for this paper were made in ink by Dr. Arnold Graf. 



MARINE BIOLOGICAL LABORATORY, 

 WOODS HOLL, MASS. 

 July 15, 1897. 



