64 



bulletin: museum of comparative zoology. 



EXPLANATION OF PLATES. 



All figures were drawn with the aid of Abbe's camera lucida, unless otherwise 

 stated in the explanation of figures. 



Arabic numerals in the figures designate rings, which, except in the case of Fig- 

 ures 23 and 27, Plate 6, are numbered from the extreme anterior end of the body 

 backward; Komau numerals designate somites numbered in the same manner. 



ABBREVIATIONS. 



act. 



Acetabulum (posterior sucker). oc. 



Eye. 



