Ex'planation of Plate AVI 



PI. XVI. Figs. 1-13 are further examples of ^ ehitinous plates, 

 viewed in the same way. The posterior end of these plates is in 

 each case ui^permost. 



Figs. 14 to 21 are views of the copulatory seals found on the 9 ? 

 after pairing. Though these structures exhibit a certain degree of 

 constancy in each species they are often scarcely distinguishable in 

 species which are closely allied and therefore are of little use in just 

 those t-ases where small recognisable peculiarities would be of value. 



The magnification varies from about eight to twelve diameters, but 

 as the actual size of the organs illustrated is not of much systematic 

 importance I have not thought it necessary to state the magnification 

 in each case. 



