189 A HISTORY OF RECENT CRUSTACEA 
CHAPTER XII 
TRIBE II..—THALASSINIDEA 
THE carapace is short and compressed, with little or no 
rostrum. The last segment of the trunk is articulated 
with the preceding. The eye-stalks are small. Both pairs 
of antennz have long peduncles. Of the trunk-legs the 
first pair are perfectly or imperfectly chelate, the last pair 
are short, more or less abnormal, directed backwards. 
The pleon has the segments not overlapping, with the 
side-plates feebly developed and having their hinder angles 
generally rounded. The pleopods are long, biramous, 
variable ; the swimming fan is strong. The branchie vary 
in number and form. | 
In this tribe are included four families, the Thalassi- 
nidze, Callianassidee, Axiidee, and Thaumastochelide. The 
division of the Macrura adopted by the late Mr. Spence 
Bate, into Trichobranchiata, in which the branchial plumes 
are made up of long cylindrical filaments, Phyllobranchiata, 
in which the plumes are formed by a series of foliaceous 
plates, and Dendrobranchiata, in which the branches of 
the various plumes divide and subdivide in an arborescent 
manner, does not seem practically very convenient. It 
has been already seen that two families so intimately 
allied as the Paguride and Parapaguridze would have to 
be placed, the former in the Phyllobranchiate, the latter 
in the Trichobranchiate, division. But also in the present 
tribe Spence Bate himself points out a weakness in the 
arrangement, for of the genus Callianassa he says :—‘ The 
structure of the branchiz of Callianussa is so intermediate 
in character that it may be claimed by anatomists as be- 
