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Hemiplax hirtipes (Jacq. and Lucas).
Cleistostoma (?) hirtipes Jacquinot and Lucas, Voyage au Pole Sud, Zool., vol. 3, Crust., p. 69. 1853.
Metaplax hirtipes Heller, Verhandl, d. k. zool-bot. Gesellsch., Wien, vol. 12, p. 251. 1862.
Hemiplax hirtipes Heller, Voyage der Novara, Crust., p. 40, Pl. 4, Fig. 3. 1865.
— Miers, Cat. Crust. N.Z., p. 34. 1876.
— Filhol, Mission de l'Ile Campbell, p. 385. 1885.
— Miers, Challenger Reports, vol. 17, p. 251. 1886.
— Chilton, Subantarctic Isl. N.Z., vol. 2, p. 608. 1909.
Macrophthalamus hirtipes Thomson, Ann. Mag. Nat. Hist., ser. 7, vol. 10, p. 462. 1902.
— Thomson, Trans. N.Z. Inst., vol. 45, p. 237. 1913.
This crab has given rise to much trouble, concerning both its generic position and especially its identity. The confusion is not lessened by the fact that the same specific name was independently chosen for two supposedly different species, which we now find it necessary to unite; assuming that the latter step is correct, the history of the views as to its generic position is briefly as follows:—
Jacquinot and Lucas had only a single much-damaged specimen, and could only suggest with much doubt that it was a Cleistostoma; affinities were also recognised with Macrophthalamus. Heller, without recognition of the previous work, located it in Metaplax, but later founded the genus Hemiplax for it. Miers accepted this name, but later suggested that it might be regarded as a subgenus of Macrophthalamus. Thomson has definitely located New Zealand specimens in Macrophthalamus, though considering them to be different from Heller's species. Etheridge and McCullough have accepted the genus Hemiplax, and have added M. latifrons Haswell to it. We have retained the name Hemiplax.
As regards the specific name, the problem is whether the Cleistostoma hirtipes described by Jacquinot and Lucas from Samoa is the same as Hemiplax hirtipes described from Auckland by Heller. Although we have not seen the types, or specimens from Samoa, we have united the two, and the result is the new combination Hemiplax hirtipes (Jacq. and Lucas). If, however, the two are not identical, our species is Hemiplax hirtipes Heller.
The grounds on which Heller's species has hitherto been regarded as distinct consist chiefly of the smallness of the hands of the male, whereas in many specimens the hands are much enlarged. But Heller had only small specimens, and the same is true of Miers (1876) and Hutton (MS. and named specimens), at least as far as is definitely known. We have a large series from a great number of localities, and regard males with small hands as conspecific with large-handed males; the final shape and proportions are acquired, according to this view, at a late stage of development. There seems to be no other distinguishing feature, and both types are present in collections from the same locality. The only doubtful point, which may not carry any weight, is that one large male in our collection has a large hand and a small one, evidently the result of incomplete regeneration; and the small hand does not resemble the hand of females or small males,
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but—except in size—the large hand of large males; which might possibly be interpreted to mean that the males with large and with small hands respectively belong to different species. But the course of development during regeneration is a matter on which experimental work is required, and incidentally we commend the problem to naturalists. If, however, the above interpretation be adopted without further evidence, where are the young males of the species with large hands?
There remains the statement by the Hon. G. M. Thomson (1902) that Macrophthalamus hirtipes Jacquinot and Lucas “has hitherto been confused with Hemiplax hirtipes Heller, a species from which it is quite distinct.” He added, and repeated in 1913, that Macrophthalamus hirtipes is common in Otago. The two names were included as distinct species in the Index Faunae N.Z., a view with which we disagree. We do so the more readily because in 1917 Mr. Thomson sent some specimens from Portobello to the senior author, and stated: “I am half inclined to think that this species [Hemiplax hirtipes] is only the young stage of Macrophthalamus hirtipes.…I have one crab labelled Macrophthalamus hirtipes, but it seems only a large form of those I have posted you.” We have interpreted this as a retraction of the former view, and acquiesce therein.
In three of our largest males, including a pair from Akaroa, the hands are more elongated than is usual in large males, with longer and thinner fingers; and the upper edge of the movable finger makes a noticeably more acute angle with the upper edge of the palm. The difference is sufficient to distinguish a new species if it is found to be constant in a good series. The Akaroa specimens were taken among rocks on a mud-flat near high-water mark by the junior author in 1921; they were almost white in colour, and had brilliant reddish-brown spots which showed up much more conspicuously than those of the usual dark-coloured specimens, and might well be compared with those of the shrimp Leander affinis. Such colour-differences may perhaps be the result of recent ecdysis.
Locality.—Auckland Harbour (Heller).
New Zealand, Queen Charlotte Sound (Miers).
North, South, Stewart, and Campbell Islands (Filhol).
Sumner, Dunedin (Hutton, MSS.).
Ponui Island, Hauraki Gulf (G. F. Pirritt).
Dunedin (Austr. Museum).
Wellington (Macleay Collection, Sydney).
Okarito Lagoon (C. E. Foweraker).
Stewart Island, Heathcote Estuary, Tauranga; mud flats and Zostera beds between tides (W. R. B. Oliver).
Very common on sand-banks in Otago Harbour and shallow bays along the coast. It is an active and most aggressive species.” (Thomson).
Otago Harbour (G. R. Marriner, etc).
Heathcote Estuary, Kaikoura, etc., on mud flats and Zostera beds, with Hemigrapsus crenulatus, but not extending as far altitudinally. (C.C. and E.W.B.).
Distribution.—Endemic.