v 



248 bulletin: museum of compaeative zoology. 



EXPLANATION OF PLATES. 



The drawings on Plates 1, 2, and 4 represent a magnification of 575 diameters ; 

 those on Plate 3 about 400 diameters. Projection of the image was made by an 

 Abbe' camera lucida. All figures except 3, 5, and 9 are composites of structures 

 extending through several, in some cases nine, sections. 



