242 Transactions. — Zoology. 



church ; Professor Parker and Mr. T. Butement, Dunedin ; 

 Mr. J. Eutland, Pelorus Valley; and Mr. E. Helms, Grey- 

 mouth. 



I shall now give a somewhat detailed description of the 

 external characters of P. planifrons, taking one of the Napier 

 specimens as a fairly typical one, and then briefly pointing out 

 the variations found in. other specimens. I shall do the same 

 with P. 7ico-zelanicus, taking a specimen from the Eiver Avon 

 as the type. Further detailed information will also be given 

 in a tabular form in an appendix, and brief diagnoses of the 

 two species are also added. I may explain that I have ex- 

 amined only those external characters that are usually taken 

 for the purpose of distinguishing different species of crayfish^ 

 and I have only concerned myself with the New Zealand 

 species of Paranephrops, and have not compared the genus 

 wath other genera of the Potaviobiidce — this comparison will, I 

 hope, be made by Professor Walter Paxon (to whom specimens 

 have been sent) in the second part of his ' ' Eevision of the 

 Astacidae. 



Description of Napier Specimen of P. planifrons. 



The specimen is a male, 5-25in. in length from the tip of the 

 rostrum to the end of the telson ; the greatest breadth is l-2in. ; 

 the length of the antennge is about 4in., and of the gi-eat 

 claws 4-oin. The rostrum is elongate triangular, with raised 

 margins bearing four spines on each side ; it is keeled below,, 

 and on the keel bears two median spines, which can be seen 

 from below just between the peduncles of the antennules. It 

 will be convenient to represent the spines on the rostrum by 



the formula ~^, the figures above the line giving the number 



of spines on the right and left sides respectively, the figure 

 below the line indicating the median spines on the keel below. 

 The carapace is nearly circular in transverse section, the 

 surface somewhat scabrous, most parts covered with very fine 

 hairs placed singly ; the spines and tubercles are mentioned 

 below. The short median ridge behind the rostrum begins 

 slightly in front of the posterior termination of the two lateral 

 ridges of the rostrum ; it is clearly marked in front, but be- 

 comes less distinct posteriorly, and disappears about half-way 

 between its anterior extremity and the cervical groove. At 

 the base of the rostrum on each side are two spines behind the 

 eyes ; there is a row of hairs between them and a tuft in front 

 of the anterior spine ; from the posterior spine a slight ridge 

 extends backwards about as far as the posterior end of the 

 median ridge. The spines on the carapace may for the sake 

 of convenience of reference be divided into the following, 

 arbitrary groups (see Plate X,, fig. 2) : — 



