302 Transactions. 



The inner margin of the carpus has 3 or 4 large sharp spines ; its upper 

 surface is provided with 2 irregular rows of blunt spines ; on some small 

 specimens 5 or 6 blunt spines are found on the outer surface of the carpus ; 

 in larger specimens these spines are sharp ; there are usually 4 spines on 

 the lower surface. 



The inner margin of the propod is armed with 2 rows of large sharp spines, 

 which are continued on to the corresponding margin of the dactyl. The 

 upper surface of the propod has 2 median parallel rows of spines, and 

 smaller irregularly arranged tubercles on the outer region ; the outer 

 margin has 2 parallel rows of short close-set spines. The spinulation of the 

 lower surface is very similar to that of the upper surface, except that there 

 is a tendency for the outer small tubercles to run in either 2 or 3 irregular 

 rows. 



There is always a large spine situated centrally on the posterior margin 

 of the dactyl, and also one in a corresponding position on the lower surface. 



Both the carapace and chelae are singularly free from hairs; when 

 present, they occur on the anterior side of the base of the tubercles, and 

 are not observed at a casual glance. 



Distribution of P. planifrons. 



P. planifrons can be divided into four rather ill-distinguished groups, 

 the tendency throughout being towards more slender crayfish as we go 

 farther north. 



The first group, which may be regarded as the normal, extends over 

 the central part of the North Island— the district bounded by Masterton, 

 Wanganui, New Plymouth, Whangarata, Kotorua, and Napier. The fore- 

 going description will, in general, apply to this group. 



The second, or Northern group, found north of Whangarata, is charac- 

 terized bv a greater slenderness of form, both in the bodv and in the chelae. 



The East Cook Strait group, which includes specimens from Wellington 

 (city), Marlborough, and Pelorus Valley, is marked by an approach in the 

 proportion of certain parts to P. setosus— that is, the crayfish have a short, 

 broad rostrum with 5 spines on either side, and a shorter and broader squame. 

 It is to be noted, however, that the Spring Creek and D'Urville Island speci- 

 mens have the characteristic long narrow squame and rostrum of the normal 

 North Island form. 



The last group, the Western South Island group, differs only slightly 

 from the normal group, having a slightly shorter squame, tapering from 

 half-way, and a shorter, though not comparatively broader, rostrum. In 

 some specimens of this group there is a median rostral carina.* 



Although the last two groups show an approach in certain proportions 

 to P. setosus, there is no doubt whatever that they are P. planifrons, the 

 arrangement of the spines on the carapace and chelae, and the shape of the 

 carapace and chelae, being distinctly that typical of P. planifrons. 



* When this was written I had examined specimens of P. planifrons only from 

 as far south as Ross, but had heard that crayfish, presumably P. planifrons, were to 

 be found in the Wanganui River, about twenty-five miles farther south. Recently, 

 however, I received a specimen, unmistakably P. planifrons, from Cromarty, near 

 Preservation Inlet. So we now have P. planifrons extending all along the west coast 

 of the South Island, evidently separated from P. zealandicus by the main watershed of 

 the Island. At Clifden, to the east, distant fifty miles direct from Cromarty, the 

 crayfish are the most perfectly definite forms of P. zealandicus. 



