5 Botany and Zoology. 119 
ority is observed in the absence or small size of the basal scale of the 
outer antenne—this scale existing in no Brachyura, and having a large 
between the Astacidea and the next division of Macroura, and in 
the genus Paranephrops of White, the antennary scale is quite large ; 
make a grand division among them. These are the Caripea. 
Another group, remains, in which the stoutest prehensile legs are 
tate of the third pair, and the line between these species and the 
Cates a transfer of force, which pertained to the first pair in the 
chyura, and to the first or second in the typical Macroura, to a pair 
More posterior: giving the anterior part of the body a still lower char- 
acter. These, the Panaipea constitute our third division or subtribe. 
Proaching the Mysis group, in which none of the legs are stout ci elate, 
(Sergesies, &c.) whose whole structure indicates their inferior charac- 
ter, and the low state of the forces within. 
_ the three grand divisions, ASTACIDEA, CaRiDEA and PEN#IDEA, con- 
Stituting the second series, thus mark three grades of rank among the 
Subiribe 1. Thalassinidea.—This section, as Milne Edwards ob- 
|i, includes two strongly marked divisions; one, with only the or- 
inary thoracic branchie, and a second with the addition of abdominal 
ym 
Thalassinidea Eubranchiata, the latter, the Thalassinidea Anomobran- 
a. The first group embraces three families, differing strikingly in 
peds and abdomen, as explained beyond. The second con- 
. 
