by less prominent but distinct ridges so that the transverse section is roughly quadrangular. 

 In addition a median dorsal ridge is distinct on the first, less so on the succeeding somites. 

 On the fifth somite the dorsal ridge again becomes prominent on its posterior half, and the 

 dorso-lateral ridges, which occupy the usual position on the anterior part of the somite, run 

 obliquely downwards and terminate on each side about the middle of the postero-lateral margin. 

 Each of the first five abdominal somites articulates with the somite in front by a well-marked 

 "peg-and-socket" articulation on each side. The last somite has well-marked median dorsal 

 and lateral ridges, and has, on the dorsal surface, a transverse cre.scentic groove. 



The texture of the integument is minutely and regularly reticulate and the surface of 

 the carapace presents also a coarse but shallow pitting. 



The first legs are longer by Vs than the carapace, and have the terminal segments very 

 slender. The basis is about "/a the length of the succeeding segments together, the dactylus "/j 

 the length of the propodus and about equal to the carpus. The propodus bears three or four very 

 long and slender setae on its lower edge and the dactylus also carries marginal and terminal setae. 



The remaining pairs of legs do not differ greatly from those of C. australis, figured by 

 Sars, except that the second pair are relatively shorter. 



The uropods (PI. I, fig. 3) are stout, the peduncle a little longer and the rami a little 

 shorter than the last somite. The peduncle is obscurely serrated on the outer and more distinctly 

 on the inner edge. The rami are of equal length, each tapering to a sharp point without any 

 terminal spine. The endopod is serrated on both edges for rather more than half its length, 

 the terminal portion being smooth. A spine on the inner margin marks the end of the serrated 

 part and there is a second small spine a little way on the proximal side of the first. The 

 exopod is obscurely serrated on both margins and is without spines or setae. 



Occurrence. Station 164, 32 metres. Two immature females. 



Remarks. By its stongly sculptured carapace this very handsome .species is at once 

 distinguished from all the species of Cyclaspis hitherto described with the exception of C. exsculpta 

 described by Sars from a fragmentary specimen obtained by the "Challenger" in 7 fathoms in 

 Flinders Passage, between Australia and New Guinea. The Challenger specimen when complete 

 cannot have been much more than ^/;j the length of the larger of the "Siboga" .specimens and 

 it is just pos.sible that the differences between them may be merely differences of growth. It is 

 very improbable however that this is the case, the hooked teeth of the po.sterior transverse 

 dorsal ridge, the small size and anterior position of the lateral depressed area, the presence of 

 an additional oblique lateral ridge on the posterior part of the carapace and the trilobate 

 posterior dorsal crest being characters which appear sufficient to define the present form as a 

 distinct species. 



2. Cyclaspis Siboga: n. sp. Plate I, figs. 4 — 6. 



Description of Female with developing oostegites. Total length 16,5 mm., of which the 

 carapace occupies one quarter. 



