RANGE OF THE HERMIT-CRABS 155 
lana. The pleon is soft as in a hermit-crab, but re- 
flexed. 
That the fifth pair of legs in the crustaceans of this 
family should be folded in the branchial chambers must 
seem a very strange arrangement, unless consideration is 
directed to the advantage which may thus be attained in 
keeping the branchie clear from parasites, 
3 
Legion 2.—Pagurinea. 
The carapace is elongate, becoming weak or membra- 
naceous behind the cervical groove, which divides the 
gastric and hepatic regions from the cardiac and branchial. 
The second antennz have an acicle. The third maxilli- 
peds are subpediform, with the third and fourth joints 
elongate. The chelipeds and two following pairs of legs 
are well developed, the last two pairs are small, one or 
both being usually chelate. The sternal plastron is linear. 
The pleon is spirally twisted or extended; the tergal ele- 
ments are as a rule rudimentary. There is generally a 
single biramous appendage to the second, third, fourth, 
and fifth segments of the pleon on the left side, the first 
three of these being well-developed and ovigerous in the 
female. The sixth segment in both sexes has a pair of 
appendages. 
Common as the Hermit-Crabs are between tide-marks, 
they are also found in depths of over two thousand fathoms. 
The legion contains three families, the Cenobitide, Pagu- 
ride, and Parapaguride. ‘The first two of these families 
are phyllobranchiate, that is, have the branchial plumes 
formed by a series of foliaceous plates, whereas the third 
family is trichobranchiate, having the branchial plumes 
made up of long cylindrical filaments. 
Family 1.—Cenobitide. 
The first antennz have a very elongate peduncle, its 
first Joint deflexed and as long as or longer than the eye- 
stalks, the second and third joints narrow and cylindrical ; 
one of the flagella enlarged. In the second antennz the 
