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THE VOYAGE OE H.M.S. CHALLENGER. 
spine at the inferior and inner lobe of the orbit, which lobe attains the front, so as to exclude 
the antennae from the orbital cavity. The peduncular joints of the antennae are small and 
slender; the basal joint does not nearly reach the front. The exterior maxillipedes are 
small, the ischium-joint not produced at the antero-internal angle ; the merus with the antero- 
internal angle obliquely truncated, scarcely, if at all, emarginate, the antero-external angle 
not produced. The chelipedes in the adult male are subequal, and considerably developed; 
merus with the antero-external angle dentated or spinose toward the distal extremity ; 
carpus without spines, palms somewhat compressed, smooth ; fingers distally acute, with 
small teeth or granules near the base ; the dactylus sometimes with a larger, granulated, sub- 
basal lobe on the inner margin ; the ambulatory legs are small, with the joints slightly 
compressed, the dactyli hairy and rather shorter than the penultimate joints. 
The species are small, and commonly inhabit the coral reefs of the Indo-Pacific 
region. They are connected one with another by almost insensible gradations of form 
and colour, hence their discrimination is extremely difficult, as shown by Dr. B. 
Kossmann, 1 who, indeed, would apparently regard all, except perhaps Trapezia digitalis, 
Latreille, as varieties of a single species. 
In the following enumeration of the described species I have grouped them mainly 
according to the presence of the lateral epibranchial tooth, by the form of the chelipedes, 
and according to their colour- variations ; but I would not be understood as regarding all 
as distinct and well-characterised types. 
1 . Carapace without lateral spines or teeth : — 
(1) Carapace neither spotted nor areolated. 
Trapezia digitalis, Latreille = Trapezia leucodactyla, Ruppell. 
Eed Sea. 
Trapezia formosa, Smith. Pearl Islands, Bay of Panama. 
(Perhaps not specifically distinct from Trapezia digitalis). 
(2) Carapace areolated. 
Trapezia speciosa, Dana. Paumotu Archipelago, Carlshoff 
Island. 
(3) Carapace spotted. 
Trapezia bella, Dana. Paumotu Archipelago, Carlshoff Island. 
2. Carapace with a spine or tooth in the middle of the lateral margins (the lateral 
epibranchial tooth) : — 
(1) Carapace and limbs of a uniform colour, without spots or areolse. 
1 Zool. Ergebn. einer ReiseKiistengeb. d. rothen Meeres, Malacostraca, pp. 11-15, 1877. 
