300 



Transactions . 



VI. Carina on Rostrum. 



There is a median keel extending forward from the cervical groove as 

 far as the anterior of the post-orbital spines (group A) in all specimens 

 of P. planifrons. This keel is continued anteriorly to about half-way 

 along the rostrum in specimens from Richmond, Murchison, and Peloids. 



VII. Spines on Rostrum (column 5). 

 The most usual number of spines on the rostrum is 4 on each side, with 

 1 or 2 below (occasionally or 4). Specimens from the Eastern Cook Strait 

 district have often 5 spines on each side, and this shows an approach to 

 P. zealandicus. The northern specimens (Puriri and Manukau) have only 3 

 on each side. 



VIII. Rostrum Length in Proportion to the Length of the Peduncle of the 



Antenna. 



The rostrum terminates level with or slightly beyond the peduncle of 

 the antenna in all but the Western South Island group, where it reaches 

 onlv to half-way along the last segment of the peduncle. 



IX. Antenna! Scale. 



(a.) Length' in Proportion to the Total Body Length (column 6). — The 

 length of the antennal scale varies in accordance with the locality. It is 

 shortest in the Eastern Cook Strait group (8-4 average proportion), longer 

 in the Western South Island group (7-8), considerably longer in the ordinary 

 North Island group (6-6), and exceptionally long in the Manukau speci- 

 mens. The proportionate length of 

 the squame in the Eastern Cook Strait 

 group is less than m P. setosas. 



(b.) Squame 4- Peduncle (column 7). 

 -The figures here show that the 

 squame is shorter than the peduncle 

 in the Western South Island and the 

 Eastern Cook Strait groups, while in 

 the ordinary North Island forms the 

 squame is slightly longer. 



(c.) Shape (fig. 3). — The squame is 

 normally long and narrow, tapering 

 from the posterior third. The varia- 

 tions found are that the Eoss speci- 

 mens were slightly broader (they 

 Fig. 4. were very large crayfish); these from 

 Murchison were very distinctly short 

 Fig. 3.— Antennal scale of P. planifrons ; and broad, two small specimens hav- 



x 3 - ing an almost semicircular squame. 



Fig. 4.-Antennal .scale of P tenuicornis mth th e tion of the g m 



Dana (after JJana). ~. , r i -n n , i ° 



Creek forms, the Eastern Cook Strait 



group showed a slightly broader squame, in which the broad appearance 

 was somewhat accentuated by the tapering not commencing till nearly 

 half-way along its length. The Manukau and Puriri crayfish had excep- 

 tionally long antennal scales. 



The opportunity is taken here to refer to Dana's (1855) drawing and 

 description of the squame of P. tenuicornis {=P. planifrons), said to have 



Fig. 3. 



