391 



Notes on Australian Isopoda. 



By Chas. Chilton, M.A., D.Sc, M.B., CM., LL.D., 



F.L.S., C.M.Z.S., Professor of Biology, Canterbury 



College, New Zealand. 



(Communicated by Edgar R. Waite, F.L.S.) 



[Read October 11, 1917.] 



(a) The Genus Serolis, Leach. 

 Figs. 1-14. 



The following notes on the Australian Serolidae are 

 based on the examination of a small collection belonging to 

 the South Australian Museum, Adelaide, which has been 

 kindly sent to me for investigation. Most of them were 

 collected in Gulf St. Vincent by Dr. J. C. Verco, and the 

 remainder by a private party of which Mr. Edgar R Waite, 

 Director of the Museum, was a member. 



The Serolidae form a peculiar family of the Isopods con- 

 taining the single genus, Serolis, with about 25 species. They 

 are characterized by the much-depressed body, round or oval 

 in form, with widely-developed epimera. The first peraeon 

 segment has the epimeral portion very largely developed and 

 produced forwards so as to enclose the head shield on both 

 sides. Beddard considers this first segment to be formed by 

 the dorsal fusion of two segments, i.e., those bearing the 

 maxillipeds and the first pair of legs (gnathopods) ; in some 

 species there is an incomplete transverse suture on the first 

 epimera which "seems to mark the line of division betweeu 

 the two segments dorsally" (Beddard: 1884, p. 8).(D The 

 terminal segment of the peraeon is vestigial, its tergum being 

 unrepresented and its appendages smaller than those pre- 

 ceding. The pleon consists of three free segments and a 

 caudal shield. In the appendages the first pair of legs are 

 developed into characteristic subchelate gnathopods, and the 

 second pair in the male may also be subchelate, though of 

 very much smaller size than . the first ; the remaining pairs 

 of legs are of the usual character, and are used for walking, 

 or perhaps also to some extent for swimming. In the pleon 

 the first three pairs of pleopoda differ markedly from the 

 fourth and fifth, and form flat leaf-like swimmerets abund- 

 antly provided with hairs. The fourth and fifth are 

 branchial, and consist of a basal joint with lamellar outer 



(l) The references are made by the year of publication to the 

 list a.t end of this paper. 



