54 



THE ROYAL SOCIETY OF CANADA 



tinctly marked off at the sides and separated from the posterior margin 

 of the carapace by a distinct notch. This portion of the body is 

 marked with numerous transverse Hues and terminates in two siiort 

 spines that project sHghtly beyond the carapace on each side of its 

 median spine. 



Stage II. In the second stage (Fig. 8) the outHne of the carapace 

 is more uniformly oval than in the first stage, and is distinguishable 

 by the much greater number of its plates and by the increased size. 

 Five examples taken at random gave the following measurements: — 



The carapace has usually an oval form and the two portions 

 recognizable in the earlier stages are still to be made out though less 

 distinctly, only one of the narrow transverse bands now persisting 

 in its entirety. In both regions there is a great 

 increase in the number of plates, those of the 

 earlier stage having been divided into from two 

 to five portions so that the total number of 

 plates is something over one hundred and eighty, 

 i.e. three times the number present in the 

 earlier stage. Anteriorly axial, marginal and 

 intermediate plates can be distinguished, but 

 their arrangement is almost too complicated for 

 description, indeed, it is not possible to deter- 

 mine from which of the original groups certain 

 ^g plates have been derived, and furthermore there 

 seems to be some variation in the details of 

 arrangement. In the posterior portion the 

 terminal spine still persists, but the sides now 

 bear six or seven denticulations. The pair of 

 sensory pores towards the anterior part of the 



carapace is also persistent and in addition there 



Fig. 8. Hansen's T larva. • ^u • .1 ^ • ^ r ^u 



c TT r -^ , IS another pair near the posterior part 01 the 



Stage II from dorsal . . t- r- 



surface. s, sensory anterior portion. 



pore. The posterior portion of the body of the 



larva is even more distinctly constricted from 

 the carapace than in the earlier stage, and as before terminates 

 in two short spines which project beyond the hinder edge of 

 the carapace, one on either side of the terminal spine. Only 

 the three pairs of naupliar appendages are present, the anten- 



