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Squilla armata Milne-Edwards.
Squilla armata Milne-Edwards, Hist. Nat. Crust., vol. 11, p. 521, 1837; Gay, Hist. de Chile, Zool., vol. 3, Crust., p. 223, 1849; Miers, Ann. Mag. Nat. Hist., ser. 5, vol. 5, p. 25, 1880; A. Milne-Edwards, Mission du Cap Horn, p. F53, 1891; Chilton, Trans. N.Z. Inst., vol. 23, p. 60, 1891; Whitelegge, Memoir Aust. Mus., vol. 4, pt. 2, p. 199, 1900; Stebbing, South African Crustacea, pt. 2, p. 45, 1902; Bigelow, Proc. U.S. Nat. Mus., vol. 17, p. 515, figs. 9 and 10, 1895. Chloridella armana, M. J. Rathbun, Proc. U.S. Nat. Mus., vol. 38, p. 609, 1910.
Specific Diagnosis.—“Eyes large, triangular, dactylus of the reptorial limb with 7 to 9 teeth; rostrum narrowed in front with a slight median elevation; carapace with median carina obsolete or entirely absent, intermediate and lateral carinae present only on the posterior lateral lobes, anterior lateral angles produced into acute spines; lateral spines of the 5th thoracic segment narrow, straight, and acute, the lateral processes of the next two segments broadly rounded and produced into spines that point backward; 8 carinae on the abdominal segments; telson with a crest and a keel and a series of curved lines of pits on each side, 6 marginal spines, the submedian pair with movable tips, no submedian denticles, 10 to 11 small intermediate ones, and I lateral one.” (Bigelow.)
Fig. 1. —Squilla armata. Telson and uropod.
Length of largest specimen examined, 135 mm.; usual length, 60–80 mm.
This species is probably common in New Zealand seas, though it is only occasionally met with, most of the specimens in local museums having
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been obtained from the stomachs of fish. I have seen specimens that were dredged in Wellington Harbour (T. W. Kirk); two fine specimens from Petone Beach, now in the collection of the Dominion Museum; others obtained during the “Nora Niven” expedition, in the stomach of a Dasybatus (Waite); two specimens from Kaikoura, in the stomach of an Alepisaurus ferox (A. D. Goodall). It has also been recorded from the Auckland Islands by Miers.
Distribution.—Widely distributed in southern seas, having been recorded from South America, South Africa, and Australia.
Remarks.—The specimens examined agree closely with the brief diagnosis given by Bigelow as quoted above. The median elevation on the rostrum is hardly appreciable, and the carinae on the carapace are only very slightly marked, especially in the smaller specimens. The submedian spines on the telson have movable tips, as described by Bigelow, in the smaller specimens, but in larger specimens the tips have become obsolete or been worn off. The curved lines on the sides of the median carina of the telson are fairly distinguishable, though the surface itself is quite smooth.
My specimens agree also with the more detailed description given by Bigelow, except that in smaller specimens the intermediate and lateral carinae do not end in spines in the four or five anterior abdominal segments; “the 1 to 4 small spines halfway between the median and intermediate carinae” on the posterior margin of the 5th segment of the abdomen appear to be constantly present.
In the characters of the telson and in some other points this speciese appears to approach pretty closely to Squilla lata Brooks from the Arafura Sea (see fig. 1).
Fig. 2— Squilla armata: Endopod of first pleoped of male.
Milne-Edwards, in the “Mission du Cap Horn,” considers S. gracilipes as probably a variety of S. armata, and certainly, as he points out, the number of spines on the dactyls of the raptorial limbs is subject to variation, so that the possession of 10 in S. gracilipes is not sufficient in itself to distinguish it from S. armata; but Miers describes S. gracilipes as having 26 denticles (i.e., 13 on each side) between the submedian marginal spines, and about 18 on each side between the submedian and the first lateral spines. In none of the adult specimens of S. armata that I have been able to examine are there any denticles between the median fissure and the submedian spine except in one instance where there are one or two small traces of a denticle, and Bigelow has drawn attention to the same fact, so that in this point there is a pretty considerable difference between S. gracilipes and S. armata; and there are other points drawn attention to by Miers which make it difficult to consider these two forms as specifically identical.
I have one small specimen, collected at Summer, that is only 20 mm. in length; but since it has the submedian and lateral carinae faintly marked on the posterior abdominal segments, and ending in spines on the 6th
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segment, it must, I think, belong to S. armata. In it the terminal segment shows little or no median fissure, and there are 12 small sharp teeth on each side between the median line and the submedian spine, and 16 between the submedian and lateral teeth, all these teeth being sharply pointed and occasionally irregular, with a small one in between two of the ordinary size. The raptorial limbs on each side bear 7 teeth on the dactyl.
In the character of the terminal segment and also of the uropods this small specimen appears to agree closely with Miers's description and figure of S. gracilipes; that species, however, is much larger—viz., 85 mm. long (“3 ⅓ in.”)—and presumably adult, and the dactyls of the raptorial limbs bear 10 teeth.
As Bigelow has pointed out, there are no secondary sexual differences in S. armata. The endopodite in the first abdominal appendage in the male is specially modified in the usual manner, and, as this appendage has not been described in this species, I represent it in fig. 2. It will be seen that it conforms closely to the type found in other species of Squilla, and a detailed description of it appears to be unnecessary.