Classification of the Thalassinidea. 549 
will rise to 23. The number of species is about 125, these, 
like the genera, being more numerous in the more specialized 
family Callianasside than in the others. The greater number 
of the species in all the families are Indo-Pacific. The 
Species are generally restricted to one region, but the genera 
are well distributed, showing no tendency to restriction to 
particular regions in any case except that of the little genus 
Glypturus from the West-Indian region. Most of the known 
species live in shallow water, but, with the exception of 
the widespread Calocaris Macandree, the deep-sea forms 
(below 200 fath.) can conveniently be arranged by means of 
the same set of regions; and this has been done above. 
The deep-water species are chiefly concentrated in Hiconaxius, 
Iconaxiopsis, Paraxius, and Calocaris, which have no shallow- 
water forms, but there are a few scattered among the other 
genera, and these have been noted in the lists. Thalassina 
anomala makes its burrows on land, but they probably always 
go down to water. 
Key to the Families ef the Thalassinidea. 
I. No linea thalassinica. Both movable and fixed 
antennal thorns present, though sometimes mi- 
nute (? absent in Scytoleptus). Abdominal pleura 
ITER Ree osdaucsenucob od Oed a obomee cee ob an 
I, ‘Bien thalassinica present (except in Calhanidea). 
Fixed antennal thorn wanting, scale reduced to 
a flattened vestige or wanting. Abdominal pleura 
usually small. 
1, Sutures on both exopodite and endopodite of 
last limb. Abdominal plewra of a good size.. Laomediide. 
2. No sutures on the last limb. Abdominal pleura 
small. 
a. Second leg chelate or simple. No podo- 
branche on legs. Abdominal limbs 3-6 
broad. <A vestige of antennal scale remains, Callianassidze. 
b. Second leg subchelate. Podobranchs on legs 
1-3. Abdominal limbs all narrow. No 
vestige of antennal scale ......... Fence ne Thalassinide. 
Key to the Genera of the Axiide. 
I, A suture on the exopodite of the last limb. [An- 
tennal thorns present, large or small.] ; 
1, Eyes pigmented. Back flat. No keel in the j 
hinder part of the carapace at least.......... Axiopsis. 
2. Fyes pale. Back arched. A keel runs the 
whole length of the carapace in the middle 
Axiidze. 
one ieee rat fac me eine Cicigoicacye nicicm  CenCeNe Calocaris, 
II. No suture on the exopodite of the last limb. 
1. Back not falling steeply to rostrwm. Antennal 
thorns present, large or small .............. Axius. 
2, Back falling steeply to rostrwm. Antennal 
Phas Lost (Pye ere istopes selsins erwetealeleyyt | ....  Sceytoleptus, 
Ann. & Mag. N. Hist. Ser. 7. Vol. xii. 36 
