t he Sout h Australian Sat iiralist. 
(A 
habits of the smooth pebble-crab 
{Philyra faevis Bell.) 
By Herbert M. Hale. 
^ 'i’he Pebble-crabs belong to a tribe of the Brachyura (the 
!/‘short tails’’, or the true crabs) termed the Oxy stomata. As the 
name indicates sharp and stovia, a mouth) the members of 
^ that tribe agree in one salient feature, namely, the mouth frame 
ia*ds narrowed in front and subtriangular in shape. The sharp- 
mouthed crabs burrow in sand or mud and the elongated mouth 
parts are the result of this habit. In the Pebble-crabs the canals 
conveying water tO:and from the gill-chambers (both the exhalent 
and inhalent channels) are prolonged to the front of the head, so 
ij-lthat the crabs are able to bury themselves in fine silt with only 
^ the extreme front exposed. 
k , The Smooth Pebble-crab occurs plentifully in the Bay of 
pi Shoals, Kangaroo Island, and during a visit to this locality the 
^ author spent some interesting hours observing its behaviour. The 
# Bay of Shoals is a shallow, extensive and protected bay on the 
north coast of the island; at low^ tide a huge area of mud flat 
is exposed and the water near shore is nowhere more than a few 
inches in depth. The picture reproduced in fig. I gives an indica- 
tion of the extent of flat uncovered at low tide. In taking this 
photograph the camera was pointed shorewards; the fringe of 
vegetation at the base of the hills in the background represents the 
. high tide limit. This tidal flat is the haunt of innumerable forms 
of life, worms, crustaceans, molluscs and other invertebrates being 
present in abundance. In the very shallow^ inshore water, the 
. Pebble-crabs commence their activities as the tide runs out and 
may remain buried in the mud at high water and during rough 
weather. The crabs w^ere mating at the time of the visit and 
’ their courting behaviour was considerably amusing. A male 
selects a female and for a time moves around the darling of his 
heart in a clumsy sort of dance; after a time the female, as if fas- 
cinated, folds her legs and remains quiescent. The male then 
seizes his consort with one or the other of his large chelipeds and 
bears her off in triumph at arm’s length, the female remaining all 
the time quite motionless. As showm in the illustration (flg. 2) 
the sexes are readily distinguished, for the males are of larger 
size than the females and have larger chelipeds. If a couple were 
disturbed during theii^ elopement the)^ at once commencecl to bur- 
row in the mud, the male placing himself immediately behind the 
female, often witli his arms half encircling her. The burrowing 
occupies only a few seconds. The initial movement is a quick tilt- 
ing upwards of the front, so that the crab rests In an upright 
position, suppprted by the walking legs; then these limbs disappear 
