's RIJKS MUSEUM VAN NATUURLIJKE HISTORIE — LEIDEN. 81 



and by the last joint of the peduncle of the inferior antennae being 

 considerably larger than the preceding joint, at least in full-grown spe- 

 cimens of about 15 mm., whereas in Orchestia the difference in length 

 between these two joints is much less pronounced. Besides, the middle 

 joints of the last pereiopods are not at all expanded, as in the males of 

 our common littoral Orchestia-s^ecies. 



The figure of Talorchestia brito here given (pi. Ill) may serve to 

 elucidate many further points of differences. It is needless to describe 

 the various parts at length, as this has been accomplished by Stebbing 

 in a quite satisfactory way. In a few points however my specimens did 

 not entirely answer to his description. Stebbing says, that the fourth joint of 

 the peduncle of the lower antennae „is not very much shorter than the 

 long fifth joint", but I found the latter more than twice as long as the 

 preceding joint, and not parallel-sided, but constricted at the base, widened 

 in the middle-third of its length and again, but very slightly, diminishing 

 in breadth towards the distal end. In the flagellum of these antennae 

 I counted 27 — 28 joints (not 30 or more — Stebbing) ; the proximal 

 five of these are slightly, if at all, separated one from another, the last 

 joint is narrow, subcylindrical and provided at the top with a tuft 

 of short hairs. In all the joints but the last one we find on either 

 side a short hair, but when examined with strong magnification this 

 hair, in the upper as well as in the lower antennae, proves to consist 

 of a bunch of 2 — 4 stiff spinules, closely fitted together, curved towards 

 the end of the joint and slightly crenulated at the fore margin near 

 the tip; the tips of the spinules of the same bunch are always in 

 close contact, but in the upper antennae they are somewhat twisted 

 round each other. 



The shape of the side-plates may be seen in the figure; I shall only 

 remark here, that the hind margin of the second to fourth plate shows 

 a prominent knob somewhat above the middle of the margin, which 

 feature is also shown in Stebbing's figure of the side-plate of the second 

 gnathopod, on his pi. XY. As such a structure is found likewise in 0. 

 gammarellus and T. saltator it cannot be used as a distinctive character. 



The carpopodite of the first gnathopod has at its hind margin near 

 the distal end a very remarkable pellucid bubble-like process, about 

 which Stebbing rightly remarks: „as this projects among various spines, 

 the impression produced at first sight was that of an actual bubble 

 of water entangled among the spines." The hand of this gnathopod 

 is rendered subchelate by a similar but less sharply defined and broader 

 process at the hind margin. The powerful and large, irregularly-oval-shaped 

 hand of the second gnathopod has been fully described and figured by 



(3-V111-1916) 



