CRUSTACEA. 
By BALDWIN SPENCER, M.A., Professor of Biology, and T. S. 
HALL, M.A., Assistant LecUirer and Demonstrator of Biology 
in the Melbourne University. 
(Plates 20, 21, 22, 23). 
Introduction. 
The following account deals with the collection made during the course of the 
Horn Expedition, and also with other foiTiis secured by one of us during a sub¬ 
sequent visit to Charlotte Waters. We are also indebted to the courtesy of the 
authorities of the Adelaide Museum for the opportunity of examining the speci¬ 
mens secured during the Elder Expedition, to Professor Tate and Mr. Zietz for 
specimens from their own collections, and to Mr. P. Squire, of Alice Springs, for 
the first specimens of Limnadopsis squirei which were secured. 
The Crustacea collected naturally vary to a great extent with the season, and 
to secure certain forms, such as Apus and some of the Estheriadaj, it is essential 
to be on the spot shortly aftei’ rain has fallen, because even if water does remain 
in the deeper pools, only particular species remain alive, the others being only 
represented by empty carapaces. 
During the Horn Expedition, which extended over the dry months from May 
to August, we only obtained living specimens of Astacopsis bicarinatus, Telphusa 
transversa and Estheria packardi. The remnants of a single indistinguishable 
carapace of one of the Apodidie (abdomen wanting) was found, and dried carapaces 
of Estheria lutraria, E. dictyon and of Limnadopsis squirei. Immediately after 
rain Apus australiensis is to be found in hundreds in small clay-pans and pools in 
the creek beds—in fact anywhere where there is water which is clouded with 
mud particles. 
The same is true, except as regards numbers, of the two species of the new 
genus Limnadopsis, and also of Estheria lutraria. 
In the Macumba Creek, for example, when the muddy flood waters occupied 
the broad bed Apus and the two species of Limnadopsis were found; but only ten 
