AN AFFECTIONATE SQUEEZE o57 



of Ike 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 Gnathiidae, 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 Serolida3 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. 



S&rolis, 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 Onisciis ]?aradoxus by Fabricius 

 in 1775, and afterwards transferred by him to his genus 

 Gi/mothoa. In 1833 Eights described Brongniartia trilohi- 

 toides, from Patagonia. By Milne-Edwards and Audouin 



