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Leptomithrax australis (Jacquinot and Lucas).
Maia australis Jacquinot and Lucas, Voyage au Pole Sud, Zool., vol. 3, Crust., p. 11, Pl. 2, Fig. 1. 1853.
Leptomithrax australis Miers, Cat. Crust. N.Z., p. 7. 1876.
— Filhol, Mission de l'Ile Campbell, p. 361. Pl. 38. 1885.
— Chilton, Subant. Isl. N.Z., vol. 2, p. 607. 1909.
— Thomson, Trans. N.Z. Inst., vol. 45, p. 237. 1913.
— Stephensen, Dr. Th. Mortensen's Pacific Exped. 1914-16, vol. 40, p. 292. 1927.
(Not L. australiensis Miers, Ann. Mag. Nat. Hist., ser. iv, vol. 17, p. 220).
The genus Leptomithrax is most readily distinguished from Paramithrax by the presence of tubercles but no ridge on the wrist of the former, while the wrist of the latter is strongly ridged. In young Leptomithrax (about an inch in length), there is, however, a nodulous ridge. The differences between L. australis and L. longimanus are very distinct and may be stated as follows:—
| L. australis. | L. longimanus. | |
|---|---|---|
| Spine at outer corner of orbital cavity | With small accessory spine at base. | Without accessory spine. |
| Granules on arm and wrist | On upper and outer surfaces only. | Over the whole of the joints. |
| Inner edge of fixed finger | Denticulated for more than half the length, the denticulations extending over the broad curve at the middle into the excavation in the proximal half of the finger. | Denticulations stopping short at the middle of the finger, where the excavation begins; end of the excavation sharply angled. |
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In addition, the arms and hands of L. longimanus are much longer, the legs are stouter, and the branchial regions more inflated at the sides than in the case of L. australis.
In young specimens and in the female, the fingers fit closely together along their whole length; there is neither excavation nor inner tubercle.
In his copy of the N.Z. Journal of Science, vol. 1, Hutton has deleted this species from the list of those whose occurrence he formerly considered doubtful; and in Miers' Catalogue he has appropriately noted that the carapace is “spinulose” rather than “covered with smooth tubercles.”
Locality.—Auckland Islands (Jacquinot and Lucas, Stephensen); “Aurora” (specimens in the Canterbury Museum).
Dunedin (Hutton).
Hauraki Gulf, 50 fathoms (G. E. Archey).
“Not uncommon on the coast (Otago). Occasionally taken on the sand-banks by the seine net.” (Thomson).
Off Little Barrier, 35 fathoms (C.C.)
Distribution.—Endemic.