AN AFFECTIONATE SQUEEZE 9 Fi 
of the six preceding pairs of limbs. The first three pairs 
of pleopods are natatory, the fourth and fifth branchial. 
The uropods are lateral, and comparatively small. The 
marsupium consists of four pairs of plates, formed probably, 
as in the Gnathiidee, by the separation of the ventral cuticle 
from the hypodermis. 
In strong contrast with the preceding family the pre- 
sent contains but a single genus. ‘This, however, is a 
strikingly well-marked type, which has excited unusual 
interest by an external resemblance to the extinct Trilo- 
bites. It is disappointing that, except in the general 
shape of the body and to a certain extent in the character 
of the eyes, nothing has been found to substantiate any 
close relationship between the two groups. A similarity 
in their habits is probable, but that might account for 
general resemblance apart from relationship. Professor 
Studer says of the Serolide that they ‘live by preference 
on sandy ground, into which they burrow with their flat 
bodies up to the caudal plate. Their nourishment appears 
chiefly to consist of the organic materials distributed in 
the fine sand, diatomacea and organic detritus. Their 
locomotion is carried on less by swimming than by back- 
ward movements on the sandy ground, wherein the widely 
separated feet are used as the point of support.’ The male 
is often but not invariably larger than the female. In 
grasping his partner by the front rim of the carapace 
with the claws of his second gnathopods, he sometimes, 
according to Studer, drives his over-affectionate nails 
through the tender chitinous integument of his beloved. 
Serolis, Leach, 1818, now contains, besides five doubt- 
ful species, seventeen that are well ascertained, nine of 
which were instituted by Mr. F. E. Beddard in his Report 
on the Isopoda of the Challenger. The first gnathopods 
have the sixth joint or hand fringed with very peculiar 
spines of two kinds. The type-species is Serolis paradoxa 
(Fabricius), at first named Oniscus paradoxus by Fabricius 
in 1775, and afterwards transferred by him to his genus 
Cymothoa, In 1833 Eights described Brongniartia trilobi- 
toides, from Patagonia. By Milne-Edwards and Audouin 
