CRUSTACEANS water in which they dwell, from time to time the maternal valves form a special case in which eggs of a particular character can be laid. These encapsuled eggs require to be fertilized by the male. At the time of moulting the cases are detached from the rest of the exuviated structure, and may lie for a long period in dried mud, preserving the eggs not only from death but also from premature development, till water reappears in which they can safely be hatched. In Eurycercus lamellatm this ephippium is designed, it appears, to contain a large number of winter eggs, Weismann having found as many as eight, Schodler from two to ten, and Mr. Scour- field having seen as many as thirteen in one of the ephippial females sent him by Professor Sars.* Among the three remaining species Acroperus harpae, Baird, is distinguished by having the head carinate above. Its tail-piece is rather long and evenly shallow, sub-dorsaliy bordered with little spinules, which are separated by an emargination from the long, slender, nearly straight ungues. These have a denticle near the base and a spinule a little beyond the middle. Graptohberis testudinaria (Fischer) is well marked by the large hooded head with widely rounded rostrum, and by the two teeth at the corner where the straight ventral and sub- truncate hind margins meet one another. The caudal region tapers to the short finely setose ungues. The little Chydorus sphaericus (O. F. Moller), with its acuminate rostrum, very convex lower margin, and not tapering caudal region, is very distinct from the preceding species. The Ostracoda, or box crustaceans, which like tiny mussels hide the details of their organization witiiin the two valves of the carapace, yielded but fevr specimens out of the large number which longer and more skilful research would doubtless provide. The three or four species obtained all belong to the family Cyprididae. Erpetocypr'u reptans (Baird) is one of our largest fresh-water Ostracoda, being nearly a tenth of an inch long. As implied alike by its generic and specific titles, it is a creeper, having lost the power of swimming, but never- theless it is rather surprisingly active in its subaqueous movements when there is any loose stuff in which it can lose itself. Dr. G. S. Brady describes the colour as 'greenish with patches of lighter and darker hue, sometimes banded with orange or brown.' ^ Notodromas monacha (O. F. Muller) is a much smaller and at the same time less elongate species. The general effect in our specimens is predominantly black with pale spaces. Dr. Brady says, ' Colour pale greenish or white, transparent, with large and irregularly spread patches of deep olive green or black.' * Notodromas literally means ' one that runs on its back,' the intention no doubt being in the present instance to signify one that swims or floats back downwards. It has been already noted that members of this genus make use of the surface-film of water, to the underside of which they attach themselves in an inverted position, like flies upon a ceiling. The ventral surface of their valves has been compared to a ' boat-like plate,' but it must be understood that the plate is flat, with only the plan of a boat sketched or moulded upon it, or, as Dr. Brady explains, ' the ventral surface is bounded by two conspicuous, elevated, arcuate ridges (figs. 3, 6), one on each valve, which together enclose a flattened lozenge-shaped area." A third species appears to be Cypr'ia ophthalmica (Jurine), in which the caudal rami have the upper- most seta situate near the middle of the ramus. Another specimen, similar in general appear- ance to the preceding, but in which the caudal rami show no upper seta, may be Cydocypris laevis (O. F. Muller), in accord with Dr. Brady's figure of what in the Monograph he calls Cypris ovum (Jurine),' but subsequently identified with C. laevis.^ To represent the Copepoda, only three species of the genus Cyclops were gathered. Two of these belong to the forms which have the first antennae seventeen-jointed, C. albidus (Jurine) with caudal rami not equal in length to the two preceding segments combined, and C. strenuus (Fischer), in which the antennae are shorter than in C. albidus, but the caudal rami are fully as long as the three preceding segments combined. The third species is much less common, and differs very considerably from the other two. By most of its characters it appears to be Cyclops kaufmanni (Uljanin). But the first antennae are clearly eleven-jointed, not ten-jointed. It is possible that the number of joints may be subject to some variation, since in Dr. Brady's Monograph, fig. 6 of plate 24 shows a female in dorsal view with the left antennae eleven-jointed and the right twelve-jointed. From his greatly enlarged separate figure of the antenna our specimen differs only by the intercalation of a short joint between the large first and second joints. The little two-jointed fifth foot is in agreement with
- Journ. Quekett Microsc. Club, 220 (1902).
' Monograph of Recent British Ostracoda, Trans. Linn. Soc. xxvi, 370, pi. 25, figs. 10-14 ! P'- i^f fig. 4 (1868). ' Op. cit. 380. ' Op. cit. 379. ' Op. cit. pi. 36, fig. 8. ' Brady and Norman, Trans. Roy. Dublin. Soc. 2, iv, 69 (1889), and 2, v, 718 (1896). I 49 7
