536 Mr. L. A. Borradaile on the 
Family Axiide, Bate, 1888. 
Definition: ‘ Thalassinidea with a rostrum of good size ; 
without the groove or crack which runs lengthwise on each 
side of the cephalothoracic carapace in the other families of 
the group, and is known as the linea thalassinica; with the 
autennular flagella of a good length, the antennal scale 
present * as a movable thorn-like structure between the 
second and third joints of the antennal stalk, and an im- 
movable thorn outside the scale on the second joint; the 
first pair of legs chelate, large, unequal, the second pair 
ending in small equal chelz, the third to fifth pairs simple, 
the fifth sometimes tending to be subchelate ; no gill on the 
first maxilliped, mastigobranchs on legs 1-4, podobranchs 
on legs 1-3 +, pleurobranchs present or not; the gills tricho- 
branch, with narrow filaments ; the plewra of the abdominal 
segments well or moderately well developed ; the abdominal 
limbs 1-5 with appendix interna, their branches narrow or 
fairly broad, and the last pair of limbs with the endopodite 
unjointed and the exopodite jointed or not.” 
Genera: Awius, Axiopsis, Calocaris, Scytoleptus. 
Genus Axtus, Leach, 1815. 
Definition: “ Axiidee in which the body is more or less 
compressed from side to side in front of the cervical groove, 
so that the back in this region shows a platform, which may 
be either flat or convex, and is often marked at its edges and 
along the middle line by ridges, though these do not, as in 
Scytoleptus, end short of the rostrum in strong teeth, but are 
continued on to it, and that at about the same level and 
without a steep fall; with or without pleurobranchs, and 
with no suture on the exopodite of the last limb.” 
The genus Axius, as thus defined, contains ail the Axiidee 
whose last limb has no suture, with the exception of Scyto- 
leptus. Various groups of its species have from time to time 
been regarded as worthy of independent rank, and these, with 
another group of the same value, are kept as subgenera in 
the present scheme. ‘This course has been taken because, on 
the one hand, there are undoubtedly considerable differences 
between any two of them, aad, on the other hand, they are 
so connected with one another that it is as yet impossible to 
devise any satisfactory way of separating them into full 
genera. A number of characters seem to be of real morpho- 
logical importance, as showing a primitive condition, and 
* Perhaps not in Scytoleptus. 
+ Axius acanthus has a podobranch on the fourth leg. 
