REPORT ON THE BRACHYURA. 
297 
Family TIL Leucosiid^e. 
Leucosiens, Milne Edwards, Hist. Nat. Crust., vol. ii. p. 118, 1837. 
Leucosiidee, Dana, U.S. Explor. Exped., voL xiii., Crust. 1, p. 390, 1852. 
Afferent channels to the branchiae opening at the antero-lateral angles of the palate 
and not behind the pterygostomian regions. The carpal and following joints of the 
endognath of the exterior maxillipedes are wholly concealed by the triangulate merus- 
joint. (The intromittent sexual appendages in the male are exserted from the sternum.) 
The genera of this family are numerous, and vary remarkably in the form of the 
carapace and chelipedes. No satisfactory classification of them has been proposed. I 
have thought it advisable to establish only two subfamilies, one of which (Leucosiinse) is 
restricted to the single genus Leucosia, Fabricius, but it may be found preferable here- 
after to separate this genus more definitely under a primary section, and to regard some 
or all of the sectional divisions of the subfamily Iliinse as distinct subfamilies. 
Subfamily 1. Ilidle. 
The anterior frontal region of the carapace is not narrowed and produced anteriorly. 
No thoracic sinus is developed. 
Section I. The carapace is laterally produced and expanded, so as to cover in great 
part the ambulatory legs. The palms of the chelipedes are moderately robust ; the 
fingers compressed, not filiform (Oreophorinse). 
Genera : — Oreopliorus, Rlippell ; Spelseopliorus, A. Milne Edwards ; Tlos, Adams 
and White ; Cryptocnemus, Stimpson ; Ulilias , Stimpson. 
This section is not represented in the Challenger collection. 
Section II. The carapace is not produced over the bases of the ambulatory legs. 
The palms of the chelipedes are short and turgid ; the fingers elongated, very slender 
or filiform, incurved at the apices, and armed on the interior margins with spinuliform 
teeth (Myrodinse). 
Genera : — Myrodes, Bell ; Nursilia , Bell ; Iphiculus, Adams and White. 
Myrodes, Bell. 
Myrodes, Bell, Trans. Linn. Soc. Lond. (Zool.), vol. xxi. p. 299, 1855. 
This genus only differs from Myra (with which it is united by A. Milne Edwards 
and Haswell) in the form of the chelipedes, whose palms are much shorter than the 
fingers, and turgid, ovoid or subglobose ; the fingers are elongated and very slender ; 
strongly incurved at the tips and armed with spinuliform teeth, some of which are more 
elongated, so that the fingers are rostelliform. This remarkable peculiarity in the 
(zool. chall. exp. — part xlix. — 1886.) Ccc 38 
