Page:Transactions NZ Institute Volume 15.djvu/95
Art. II.—Further Additions to our Knowledge of the New Zealand Crustacea.
By Charles Chilton, M.A.
[Read before the Philosophical Institute of Canterbury, 7th September, 1882.]
Plates I.–III.
BRACHYURA.
Hymenosoma lacustris.
Elamena(?) lacustris, Chilton. (Trans. N.Z. Inst., vol. xiv., p. 172.)
This species was described from a single specimen, a female. I have since, through the kindness of Professor Hutton, received seven others, all males, so that I am now able to describe it more fully and to refer it to its proper genus.
In the Catalogue of the Stalk- and Sessile-eyed Crustacea of Australia Mr. Haswell has replaced the genera Hymenicus and Halicarcinus by Leach's original genus Hymenosoma; and my species will also come under this genus as it is defined in Mr. Haswell's catalogue. Its name will therefore be Hymenosoma lacustris.
Specific description:—Carapace nearly circular, rather broader than long; flat, naked, or with a few scattered hairs. Rostrum broad, strongly depressed, its upper surface concave from side to side, extremity in the form of an obtuse angle. Antero-lateral margins of the carapace with two obscure teeth. Chelæ of male small, propodos only slightly broader than the carpus, hairy. Ambulatory legs somewhat densely covered with long hairs, tarsi long, slender, compressed, densely-haired. Last pair of legs somewhat shorter than the preceding. Abdomen of male of five joints subequal in length, third rather narrower than the first and second, fourth nearly as wide as the third, last broadly rounded at the end; margin fringed with very short hairs, some longer ones being scattered on the surface. Abdomen of female with a slight median ridge along its whole length.
Hab. Lake Pupuke. (Fresh water.)
The hairs on the legs and carapace appear to be somewhat variable.
The third (external) maxillipedes are shown in pl. I., fig. 2a. On them are found setæ of several kinds ranging from the ordinary plumose setæ (c) to others strongly serrated on each side (b).
This species is remarkably near Hymenosoma australe, Haswell, from Port Phillip. From this, however, it differs in the chelæ of the male which are small, while in H. australe they are "extremely large."
Isopoda.
Genus Scutuloidea, (novum).
Generic description:—Body not very convex. Pereion much broader than the cephalon, increasing regularly in breadth up to the fourth segment and then decreasing again.