CRUSTACEA OF NEW ZEALAND. 201 



It is quite possible that on an examination of a greater number of specimens from 

 various localities the differences between P. tijpious and P. assimilis may partially or 

 wholly break down ; but, so far as my observations at present go, the Ashburton specimen 

 of P. tupicKS is practically identical with those from Eyreton and differs from P. assimilis 

 in the following points : — 



(1) The body and the appendages are much more slender than in P. assimilis. 



This character is of course only a relative one and therefore difficult to estimate 

 with accuracy, but in my specimens the differences, especially in the legs and 

 the lower antennre, are very mai'ked. 



(2) The pleura of the second to fifth pleon-segments, inclusive, are not so greatly deve- 



loped and have all the inferior margins regularly supplied with moderately stout 

 setae. In P. assimilis the pleura are considerably deeper than their respective 

 segments and have the inferior margins only sparsely fringed with spinules. 



(3) The shape of the projection at the end of the telson is quite different in the two 



species. 



(4) The shape of the lobes of the lower lip also differs to some extent. 



(5) The inner lobe of the first maxilla is broader distally and bears fully twice as 



many long plumose seta? as in P. assimilis. 



(6) There are slight differences in the second maxilla? ; thus the long plumose setse 



on the innermost lobe extend some distance along the inner margin, while 

 in P. assimilis they are pretty well confined to the extremity ; the rows of 

 setye along the inner margin of the basal portion also differ in character. 



(7) The grappling-setae of the maxillipedes also differ slightly. 



The differences in the mouth-parts are somewhat peculiar, and were quite unsuspected 

 when I had from other reasons already perceived that there were two species. The differ- 

 ences in the inner lolie of the first maxillae are very noticeable. 



Of the two, P. assimilis approaches more nearly to P. anstmlis than P. typicus does, 

 and I am inclined to think that, leaving out of account the special characters which are 

 due to their subterranean life, P. assimilis is more closely related to P. australis than it 

 is to P. typicus. The two former agree with each other and differ from P. typicus in 

 the following points : — 



(1) The stouter body and appendages. 



(2) The shape of the lobes of the lower lip. 



(3) The inner lobe of the first maxilla bears only 4 or 5 pkimose setae. 



(4) The pleura of the jileon-segments are almost equally well developed in both. 

 On the other hand, P. australis has the projection at the end of the telson rather more 



like that of P. typicus, and in the second maxillae and the maxillipedes it is also quite as 

 close to P. typicus as to P. assimilis, if not closer ; but in the last two points the differences 

 of all three species are very trivial. 



Phreatoicus australis di&ers from both the subterranean species in the following points, 

 in addition to those which are evidently due to the different modes of life: — 



(1) The body and especially the legs and pleura of the pleon are more abundantly 

 supplied with setae. 



