264 MB. G. M. THOMSON ON THE OCCCEEENCE OF 



Both forms described in this paper appear to me to be quite 

 distinct from any other species of the genera hitherto known. A 

 feature iu which they differ from all species yet described, excepting 

 Ci/claspis pusilla, Sars, is the total absence of spines, or other 

 epidermal growths, and o£ sculpturing on the carapace. 



Cyclaspis leyis, n. sp. (Plates XVI. & XVII. figs. 1-26), 



Specific Characters. — Carapace somewhat laterally compressed, 

 keeled above and slightly gibbous, smooth, destitute of ridges or 

 sculpturing. Ocular lobe hardly visible. Eye not made out 

 (wanting ?). Body slender, tapering gradually to the tail ; 

 dorsal ridge distinct, lateral ridges almost wanting. Pirst pair of 

 legs with basal joint elongated and produced into a long acute 

 appendage ; remaining five joints about as long as the base ; 

 last joint with four spines. Second pair of legs as long as 

 or longer than the third ; terminal joint armed with six ser- 

 rated spines. TJropoda with the branches subequal and rather 

 shorter than the scapes, with a fringe of setae along the inner 

 edge. 



Length of largest specimen 8 millim. 



Seen from above, the form of the body is rather slender, and 

 tapers gradually and uniformly from the carapace to the tail. 

 Looked at from the side, the carapace is considerably dilated, 

 and is evenly rounded on its upper surface. The " pseudo- 

 rostral projection " (of Sars) is short, pointed upwards, and sub- 

 obtuse. The length of the carapace is about one fourth that of 

 the whole animal, exclusive of the uropoda. The whole surface 

 of the body is remarkably free from ridges or prominences. The 

 integument is marked throughout by small rounded scale-like 

 thickenings. The colour '(in spirit-specimens) is nearly white, 

 without any pigment-spots. 



The four exposed segments of the thorax behind the carapace 

 are somewhat broader than the caudal segments, and are connected 

 with each other by flexible membranous spaces ; the epimera 

 are rounded both anteriorly and posteriorly. The abdominal 

 segments are longer than the thoracic, and are nearly uniform 

 in length, except the penultimate, which is the longest. The 

 relative length of all the body-segments on the dorsal line 

 from the front of the carapace to the end of the tail is as 

 follows : — 



