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2. Paranephrops zealandicus, White.
Astacus zealandicus, White, Proc. Zool. Soc. London, pt. 15, p. 123 (1847). Paranephrops neo-zelanicus, Chilton (in part), Trans. N.Z. Inst., xxi., p. 249 (1888). Paranephrops zealandicus, Faxon, Proc. United States Nat. Mus., vol. xx., p. 680 (1898).
In this species “the chela is much shorter and broader than in P. planifrons, and it is furnished with conspicuous dense tufts of silky hair, disposed in longitudinal rows. The upper margin of the hand is armed with a series of prominent spines, continued as a double row on the margin of the dactylus. The lower margin of the hand is furnished with a double row of shorter spinous teeth. The outer face of the hand is provided with a few tubercles, which seldom develope any spinous points; the inner face bears two longitudinal rows of short teeth. The rostrum is armed on each side with small, blunt teeth, usually five in number, but in some individuals three, four, or six; the inferior edge is either unarmed or else provided with one or two acute teeth; a median carina runs over the gastric area, ceasing abreast of the anterior pair of post-orbital spines, the rostrum proper being wholly destitute of a median dorsal keel. In small specimens the sides of the carapace are smooth, or at the most reveal only the slightest trace of low rounded papillæ; but in large specimens, that have attained a length of 115 mm. or more, the sides of the carapace are thickly studded with rounded tubercles. The
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antennal scale is rather short, and it is broadest in the middle.”
This species, as restricted by Faxon, appears to be common throughout Otago and Southland, and has been recorded also from Stewart Island.
In connection with this species, Faxon gives the result of some observations I had communicated to him on the variations in size, &c., that occur in correspondence with the quantity of water in which the crayfishes live. In small streams around Dunedin and Port Chalmers, where the flow of water is small, the specimens are all small, sexually mature specimens not exceeding 84 mm. in length, and in them the carapace is well-high destitute of spines and tubercles. In places where these streams have been dammed up to form reservoirs, such as the Dunedin reservoirs, or the small one connected with the Glendermid Tannery at Sawyer's Bay, the crayfish attain a much larger size, even up to 158 mm. in length, and in them the sides of the carapace are heavily tuberculated, the tubercles having the form of prominent, smooth, rounded papillæ.
If sexually mature specimens from the small streams and from the reservoirs are examined without knowledge of the conditions under which they occurred they would almost certainly be considered as different species by the vast majority of systematists.