The Atoll of Funafuti, Ellice group : its zoology, botany, ethnology and general structure based on collections made by Charles Hedley of the Australian Museum, Sydney, N.S.W.
Tribe Epicaridea. — Athelgue aniculi, sp. nov
Athelgue aniculi, sp. nov.
(Plate vii., fig. 5, a, b, c.)
Body oval, twice as long as broad, slightly transversely convex above and depressed below.
Upper antennas short, with two exposed joints and a short flagellum, surmounted by a pencil of setse, the last joint equal in length to the third joint of the outer antennæ;; the latter with four joints, the first short, broad and boss-like, the second stout, elongate and equal to the last, which is rather slender, third joint a little longer than broad, the flagellum is slightly longer than the breadth of the last joint and ends in a tuft of hairs.
Immediately posterior to the upper antennæ; is situated a transverse lip-like process (the frontal edge of the cephalon) which extends to between the bases of the second antennæ; and of the first pair of legs. Eyes not discernible.
The cephalic shield is separated from the frontal margin by a slight groove, its anterior edge is almost straight, the antero-lateral angles are oblique and in contact with the bases of the first pair of legs, the posterior margin is evenly rounded.
The segments of the perseon are rather indistinct ventrally, but well marked dorsally, the first segment scarcely visible behind and almost in contact with the cephalic shield, the second much longer than the first, the third and fourth equal; fifth and sixth a little longer and broader than the preceding pair, seventh equal in length but considerably narrower than the sixth.
On the posterior margins of each segment there are a pair of flat triangular teeth, directed towards the pleon, they form two longitudinal rows, and are situated nearer the bases of the legs than the median line of the body, the first and last pairs are small, the intermediate pairs subequal.
The legs are curved over towards the dorsal surface, and—excepting the first pair—are equal in length, the first five are equidistant, a rather wide space exists between the fifth and sixth. The short basal joints are tumid, and have a short lobe which is acute in the last three pairs, second joints of the fifth, page 150sixth and seventh legs, have a bead-shaped elevation on the posterior surface a little below the middle; third joints shorter than the second, and in all the legs more or less produced and lobate at the infero-distal extremities; fourth joints short, the fifth bent over and opposable to the distal lobe of the third joint, sixth joint minute, triangular, and opposed to a projection of the propodus.
The first and second segments of the pleon are as long but not quite so broad as the last segment of the peræ;on, the fourth is about half the size of the third, fifth and sixth very short and subcylindrical, the latter terminating abruptly, and bearing a pair of minute lanceolate appendages.
The pleopoda are inserted on the margins of the pleon. They are pedunculate and consist of sixteen foliate plates; the first joint is about twice as long as broad, the outer and inner rami are situated at its distal extremity, the inner ramus is obovate and almost sessile, the outer with a peduncle as long or longer than the basal joint, the lamina is subfalcate with an even curve on the outer margin, its inner straight distally and lobate proxi-mally; the fourth outer ramus is a little shorter than the peraeon.
The first pair of marsupial plates is folded in front of the head so as to produce a kind of funnel, consisting of two spout-shaped lobes; posteriorly on the ventral surface they are pro-duced and form a pair of subfalcate blades, which are evidently of a vibratory character and seem well adapted to drive a current of water through the brood pouch.
There are five pairs of functional marsupial plates, the second pair overlaps the falcate prolongations of the first pair, the posterior ciliate margins of the last and largest pair do not extend beyond the terminal segment of the perseon.
The colour of the peræ;on above and below, and of the lower surface of the pleon is light salmon yellow, the legs and the peduncles of the pleopods are yellowish-white, the pleopodal rami are opaque-white, with a few translucent lines radiating from the midrib; the anterior and posterior marsupial plates are somewhat opaque, the intermediate plates are translucent.
As the specific name implies, the host of this Epicarid is Aniculus typicus, which hermit crab invariably occupied the shell of Turbo setosus, Gmelin, and was never seen except at low water, on the edge of the outer reef most exposed to the surf, where it was rather rare. This most interesting parasite—the only one procured by the Expedition—was accidently discovered on the anterior surface of the abdomen, near the hinder margin of the carapace. The host was drowned in fresh water, and when dead was found somewhat exserted from its shell, exposing page 151the epicarid to view. In one of the bottles was a specimen of what might possibly be the male of this species, but which is too much damaged for accurate description, and it is doubtful whether it really belongs to the Athelgue.
|Length of cephalon and person||11mm.|
|Length of pleon||6mm.|
|Breadth of pleon||5mm.|
|Length of outer ramus of third and fourth pleopods, peduncle included||9mm.|