VI FAMILIES OF PAGURIDAE—BRACHYURA 181 
mated at the base; the chelipedes are equal or subequal, or the 
left is much larger. Chiefly in the warm and tropical seas, but 
Clibanarius and Diogenes also in the Mediterranean. 
Fam. 3. Cenobitidae—The abdomen is as in Paguridae. 
The antennal scale is reduced, the flagella of the first antennae 
end bluntly. The members of this family are characteristic of 
tropical beaches, where they live on the land. Cenobita, with 
about six species, in the West Indies and Indo-Pacific, living in 
Molluse shells; Birgus (Fig. 119) on Indo-Pacific coral islands. 
Fam. 4. Lithodidae.—The abdomen is bent under the 
thorax, and the body is crab-like and calcified. The rostrum is 
spiniform, and the sixth abdominal appendages are lost. 
Sub-Fam. 1. Hapalogasterinae——Abdomen not fully calcified, 
and without complicated plates. Hapalogaster and Dermaturus 
in the North Pacific littoral. 
Sub-Fam. 2. Lithodinae— Abdomen fully calcified, with a 
complicated arrangement of plates. Lithodes (Fig. 121) pyracti- 
cally universal distribution, littoral and deep sea. Acantholithus, 
deep littoral of Japan; Paralomis, west coast of America. This 
last genus should probably be placed in a separate family. 
Sub-Order 3. Brachyura.' 
The abdomen is much reduced, especially in the male, and is 
carried completely flexed on to the ventral face of the thorax so 
as to be invisible from the dorsal surface. The pleopods in the 
male are only present on the two anterior segments, and are 
highly modified as copulatory organs; the pleopods in the female 
are four in number and are used simply for carrying the eggs; 
the pleopods of the sixth pair are always absent in both sexes. 
The first antennae and the stalked eyes can be retracted into 
special pits excavated in the carapace. 
The larva hatches out as a Zoaea” (Fig. 124, A) very similar 
to that of the Anomura; it is furnished with an anterior and 
posterior spine on the carapace. It is characteristic of the 
Brachyuran Zoaea that the third maxillipede is fashioned from 
the beginning in its definitive expanded form, and is never a 
biramous swimming organ as in the Anomura. The only excep- 
' For general literature consult Ortmann in Bronn’s Tier-Reich, v. 2, 1901, p. 778. 
See also Reports of Challenger, Valdivia, and Talisman Expeditions, etc. 
2 Gurney, Quart. J. Micr. Sci. xlvi., 1902, p. 461. 
