62 
THE VOYAGE OF H.M.S. CHALLENGER. 
Scyra, Dana. 
Seym, Dana, Amer. Journ. Sci. and Arts, ser. 2, vol. xi. p. 269, 1851 ; Crust, in. U.S. Explor. 
Exped., vol. xiii. (i), p. 80, 1852. 
„ Miers, Journ. Linn. Soc. Lond. (Zool.), vol. xiv. p. 663, 1879. 
The carapace is somewhat depressed, tuberculated, but not spinose on the dorsal 
surface, and with well-developed lateral epibranchial and prseocular spines. The 
rostral spines (in the two species I have examined), are vertically compressed and 
laterally dilated at base, acute at the distal extremity. The orbits are small, with a 
lateral aspect, with a narrow hiatus or a nearly closed fissure in the upper margin, and 
a wider hiatus below. The post-abdomen, in the male, is distinctly seven-jointed. The 
eyes are very small and retractile. The basal antennal joint is moderately dilated, with 
a very small spine or tooth at the antero-external angle ; the two following joints are 
slightly dilated and compressed, and these, with the flagellum, are scarcely,- if at all, 
concealed by the spines of the rostrum. The merus of the exterior maxillipedes is 
distally truncated, with the antero-internal angle not produced, and the antero-internal 
angle notched. The chelipedes (in the adult male) are well-developed, with the palm 
slightly compressed and carinated above, and the fingers acute, with scarcely any basal 
intermarginal hiatus. The ambulatory legs are of moderate length, the joints sub- 
cylindrical, without spines ; the first pair does not much exceed the rest in length ; the 
dactyli are short, acute. 
The examination of a larger series of specimens has shown that the fissure in the 
upper margin of the orbit is sometimes open, and constitutes a distinct hiatus in this 
genus, which will, therefore, be better placed among the Maiinse, near Hyastenus, than 
with the Pericerinse, where I formerly classed it. In the form of the carapace, orbits, 
rostrum and antennae it also presents obvious affinities with the genus Hyas and its 
allies. 
Two well-marked species of this genus have been described, Scyra acutifrons, Dana, 
from the coasts of Oregon, California, British Columbia, and Vancouver Island, 1 and 
Scyra compressipes, Stimpson, from Japan (6 to 50 fathoms). 
Scyra umbonata, Stimpson, 2 from the Gulf of Florida (143 fathoms), cannot be 
included in this genus, since it differs in the cylindrical spines of the rostrum and non- 
dilated mobile joints of the antennae, and the merus of the exterior maxillipedes is not 
notched at the antero-internal angle. In the flattened protuberances of the carapace and 
in other characters this form somewhat resembles the Oriental Oxypleurodon stimpsonii 
(Miers). 
1 Specimens from the two last mentioned localities are in the collection of the British Museum. 
2 Bull. Mus. Comp. Zool., vol. ii. p. 115, 1870. 
