120 
The South Australian Naturalist. 
Excursion to Modbury, March 1st, 1924.~~Tlie party were 
most hospitably entertained, and a useful afternoon 
was spent in examining the shells and other curios 
collected by Mr. Smith, M'ho shoAved himself not only an 
ardent collector but a nature lover keenly interested in many 
branches of natural history. 
Dredging Excursion, March 15.— The weather proved 
ideal, the sea being absolutely smooth and the large party 
under Professor T. lLai*vey Johnston and .Mr. AV. J. Kimber, 
obtained abundant and \'aried hauls of a great many foniis of 
sea-life. The leaders gave interesting and informative talks 
on the material collected, and Professor T. Harvey Johnston 
subsequently dealt Avith some of the material in his lecture 
on March 18th. Mv. Herbert M. Hale, of the S.A. Museum, 
reports as folloAvs on a fcAv of the Crustaceans taken; A 
good bottom was round about six miles Avest of the Sema- 
phore, and many interesting marine invertebrates soon ap- 
peared on deck. (.'rustaceans were largely in evidence, but 
to enumerate these is beyond tlie scope of this publication. A 
few of the larger forms may, however, be mentioned. At 
almost every haul sponge-crabs Avere taken in the dredge, 
the commonest species being Cryptodromia octodcutata ; this 
(*rab sometimes carries aj*ouud upon its back a sponge several 
times its OAvn Aveight. Tavo species of spider-crabs Avere also 
lairly plentiful amongst the weed. Fragments and streamers 
of Aveed are picked up by these Ciaistaceans and fastened on 
to the upper surface of tiie carapace by means of hooked 
hairs thus very effectually disguisii^g the cn*abs. A small 
Hynienosomatid crab Avith a triangular carapace attracted 
attention by its unusual shape. It has been given a very long 
name — Elamena {Trigonoplax) ungiiiformis vajj. lougirostris; 
this crab has not before been noted for South Austi'alia. being 
X>reviously described from Victoria. 
Of the Prawns, the most strikiiAg species taken Avas the 
large Crangon bidens (formerly Alphciis) Avhicli is of ornate 
coloration. Crangon has a large cbeli])ed liml), with a trig- 
ger arrangement of the tAvo terminal joints Avith A\ hieh a loud 
click is produced. Sound-producing organs are knoAvn to 
occur in a good number of Crustaceans. A Hci'iuit crab 
recently taken by Professor AVood-Jones’ i‘>arty on Flinders 
Island has a stridulatory apparatus on the chelipeds. The 
use of these devices is not clear. Dr. Alcock lias suggested 
that in the case of some tropical crabs (Ocypodc), Avhicli live 
in holes, the stridulation possibl\- serves to indicatt' to intru- 
ders that a burrow is occupied; the vStridulatory appai'atus 
is present in the adults of both .sexes. 
