1864.]| MR. C. SPENCE BATE ON NEW CRUSTACEANS. 665 
The size of the largest female in the collection is in length about 
17 inch, and breadth about 2 inches. 
CRYPTOLITHODES ALTA-FISSURA, 0. 8. 
Female. 
This species may readily be detected from the two previously known 
by the smoothness of the carapace, propodi, and pleon, and more 
distinctly by the deep orbital notch on each side of the rostrum. 
The carapace is nearly as broad again as long, and produced con- 
siderably posteriorly to the cardiac elevation—a feature that appears 
to belong to the female. The rostrum is broad, flat, and rectangular. 
The antero-lateral margins are produced so far anteriorly as to be 
nearly in a line with the extremity of the rostrum ; a deep notch, in 
which the eyes are situated, exists on each side of the rostrum. The 
anterior margin is slightly marked with distant small points. The 
posterior margin is quite smooth and even. The dorsal surface is 
quite smooth, and pencilled in light red upon a yellowish ground, the 
red pencilling being fine and delicate, following the contour of the 
margin and surface of the carapace. 
The pleon is subsymmetrical and very smooth, and planted con- 
siderably within the posterior margin of the carapace. The second 
segment (first visible) has the marginal plates fused with the central. 
The sixth segment is without lateral plates; and the telson is si- 
tuated beneath, and anterior to, the posterior extremity of the sixth 
segment. 
The eyes are small, and placed upon peduncles that gradually taper 
from the base to the extremity. The first pair of antennze are short, 
and developed upon the type of those of the Brachyura; but the first 
joint is reduced to a size that is only about twice the diameter of the 
second. The second pair of antenne are but little longer than the 
first, and are furnished with a broad round scale at the third joint, 
and a terminal flagellum that is about the length of the fifth joint of 
the peduncle. The squamiform appendage is circular and disk-like ; 
the inner margin is straight or somewhat excavated. 
The second pair of gnathopoda have the third joint much broader 
than the fourth (the secondary appendage reaches not to the extre- 
mity of the third), and have the terminal joints small and rudimentary. 
The first pair of pereiopoda are subequal in the female, the propodos 
upon the right side being somewhat larger than that on the left ; 
the surface is smooth and even, and the dactylos is furnished with a 
prominent carina that terminates abruptly near the basal articulation, 
and loses itself gradually towards the apex. The fifth pair of pereio- 
poda are completely hid from view; the three basal joints are short ; 
the two terminal ones subequally long, and furnished with a copious 
brush of strong cilia. These appendages are folded together and 
enclosed within the branchial chambers, where they, no doubt, fulfil 
the office of the flabella of the highest forms of Crustacea—affording 
an interesting illustration of an organ being converted, by the force 
of circumstances, from its original purpose to the fulfilment of an- 
other, for which it was apparently most unsuited. 
