OCR Text |
Show 1902.] CRUSTACEA OF THE " SKEAT EXPEDITION." 375 29. D ic h e l a s p is e q u in a , sp. nov. (Plate X X X V . figs. 7-7 d.) Loc. Trenfforanu. o o Hab. Bases of antennnles, antennae and legs, and posterior border of carapace of Neptunus (Amphitrite) gladiator. The carina in this species is formed of two pieces-a quite short basal portion, and a much longer tergal portion, each of which abuts closely on the other by a small median tooth ; these two pieces can be separated readily by caustic potash. In the basal portion the base, embedded in the peduncle, is somewhat widened and forked, but the prongs of the fork are not very prominent; the tergal portion, quite narrow where it abuts on the basal, gradually widens towards its distal end which is squarely rounded. The scutum consists, as usual, of two parts, connected by a bridge of tissue semicalcified on its occludent side, completely calcified on its basal side (fig. 7 d). The occludent segment is nearly twice as long as the basal ( = 5'25 mm.: 3 mm.) and has its apex rounded ; the basal segment is twice as broad as the occludent at the middle of its length, three times as broad along its basal margin, and is produced at its rostral angle into a blunt, almost tooth-like process, forming the half-bridge of calcified tissue mentioned above. General shape subtriangular, with rounded angles ; its basal and tergo-lateral margins are somewhat convex, the occludent somewhat concave. The tergum has rather the shape of the head and neck of a horse with forwardly-directed ears (whence the specific name)- the base of the neck lying between the apices of the occludent segment of the scutum of the carina ; the top of the head forming the upper, the back of the neck the lower carinal margin ; and the snout forming a strong tooth projecting in the direction of the scutum, and the forehead forming the occludent margin. The 1st cirrus lies close to the 2nd, but yet a little more distant than the rest are from each other; the rami of each of all the cirri are equal; the 1st cirrus is only a little more than half the length of the 6th. The caudal appendage is as long as the lst^ joint of the pedicel of the 6tli cirrus ; it carries hairs at its apex of which the longest are about half the length of the joint, and 'also distant bundles of 2-3 longish hairs along the outer margin. The penis is just shorter than the 6th cirrus, thick, but tapering suddenly at the tip, with an excavation at the base, at the distal angle of which excavation is a blunt tooth-like prominence nearly as high as the excavation is deep; this prominence is set within a shallow hollow within the excavation. The penis also besides the hairs at its tip, bears along its length scattered hairs, some short and stiff, others long and more flexible; rings The palpi are bluntly conical, with longish hairs at the tip. The mandible has five teeth, the one at the inner angle being the strongest and the one at the outer angle very small and blunt, lying close to the 4th tooth at its outer base. |