THE AMPHIPODA. 



19 



Arch^oscina, n. g. 



In general habit and in tlie api:)ondages of perseon and pleon like Scina. 



Eirst antennae short and thick ; second slender, straight, ending in an elongate spine... 

 Mandibles with a three-jointed palp, in which the third joint is much the longest. All 

 three pairs of uropods with the outer branch well developed, longer than the peduncle. 

 ■ In regard to the above definition, it may be observed that the first antennse have the 

 form found in the young of species evidently belonging to Scina. It is also probable 

 that the long inner branch of each uropod is jointed to the peduncle, but this feature is 

 not exhibited with sufficient clearness in the only available specimen to be relied on as 

 a generic character. Should it be in future more positively ascertained, it will strengthen 

 the inference, drawn from the presence of a mandibular palp, tliat Archceoscina is really an 

 archaic Scina, retaining properties which other members of the family have relinquished. 

 Changes in the mode of defining the new genus will no doubt be required if further 

 examples of the species on which it is founded show a more advanced development, 

 but the mandibles will still distinguish it from all hitherto known Scinidee *. 



4. Arch^oscina Bonnieri, n. sp. (Plate 3 a.) 



The single specimen from its minuteness and the shape of its first antennte ran a risk 

 of being laid aside as a young one of some species of Scina. The material at hand for 

 comparison was not sufficient to encourage a hope that the question of such relationship 

 could be settled. On the other hand, from two specimens of about the same size, 

 undoubtedly juvenile species of Scina, the present form was distinguished bv havin"- the 

 back imbricated instead of smooth, by the numerous sensory filaments on the first 

 antennae, and the needle-like spine on the second. Dissection showed a still more 

 notable difference in regard to the mandibles. 



"Whether the first and second segments of the pera>on were distinct or partiallv 

 coalesced, and whether any eyes were present or not, could not be made out. The 

 postero-lateral angles of the first three pleon-segnients are rounded. 



The first antennae are planted wide apart. Tm o short, apparently separate, peduncular 

 joints are followed by a thick slowly tapering joint, fringed on the inner margin with 

 eight or more pairs of sensory filaments. To this succeed two small narrow joints 

 followed by a longer transparent joint with two spinules projecting from its blunt apex. 



The second antenme ajjpear to have four peduncular joints, none of them very long, 

 followed by one or two small flagellar joints and at the end the ucedle-like spine, longer 

 than all the joints of the appendage together and extending beyond the first antennae. 



Mandibles. — The exact shape and ar-mature could not be satisfactorily made out, but 

 in each the jjalp was uninjured, with second joint longer than the first, and the slightly 

 curved tapering third longer than l)oth the others combined. With the other mouth- 

 organs the dissection was not sufficiently successful to admit of description. 



The gnathupods are of the character familiar in the genus Scina, the third and fourlli 

 joints short, the fourth slightly underriding the fifth, the filth and sixth subequal in 



* "On Vagaries of iho Maudibulur I'alp iu the Hyperiida;." See pp. 34, 35. 

 SECOND SERIES. — ZOOLOGY, VOL. X. 5 



