SYSTEMATIC REPORT 29 



descriptions and figures given by Hansen and Fage, but that the other two, which were captured off 

 the south coast of Japan, differed as follows: '(1) The rostral plate has the outer antero-lateral angles 

 drawn out into conspicuous spines ; the margin between these spines is slightly concave in the centre 

 and is microscopically serrulated; there are three or four spinules on the lateral margins of the rostral 

 plate on each side and a prominent ocular spine on the carapace margin over the eye ; there are 

 also scattered microscopic spinules on the lateral area of the carapace below and behind the eyes. 

 (2) The outer margin of the antennal scale has only 

 three or four teeth in addition to the terminal tooth.' 



A glance at Fig. 1 A will show how very closely the 

 Discovery specimens agree with this description — the 

 only difference being that in them the serrations, which 

 adorn the margins of the rostral plate, would appear to 

 be coarser and probably fewer in number than in 

 Tattersall's specimens. My figure is taken from the 

 smaller of my two specimens. The larger animal is badly 

 damaged, but the margins of the rostral plate are quite 

 clear and show that there are rather more serrulations 

 than in the smaller specimen, but not so pronounced. 

 It is probable that there is considerable individual varia- 

 tion in this character. In both my specimens the outer 

 margin of the antennal scale bears only two or three teeth 

 in addition to the terminal one. 



Hansen (19 12) recorded that the apex of the telson in 

 his specimens was truncate and lacked spines or hairs, 

 adding that it was possible that these may have been lost. 

 Fage (1939, 1 941) recorded that the apex of the telson 

 in his specimens was straight and armed with four short 

 spines. Tattersall (1951) stated that both of his Japanese 

 specimens had seven spines on each of the lateral margins 

 of the telson and that in one of them the armature of the 

 apex was almost intact, showing ' four rather stout and 

 closely set spines, the inner pair nearly twice as long as 

 the outer pair '. 



The two specimens in the Discovery collection indicate 

 very strongly, at least as regards the telson, that previously 

 recorded variations can be attributed to the damaged con- 

 dition of the material available. In the larger Discovery 

 specimen all the spines of the telson are missing, but there are seven notches on each lateral margin 

 indicating where the spines were borne and the apex presents an appearance strikingly like that figured 

 by Fage (1942) for his specimen. I feel convinced that the 'four small spines' which he noticed are 

 really the broken pieces of the original armature of the telson apex. The smaller Discovery specimen 

 has the telson intact, except for the loss of one of the larger apical spines. The high serrulated keels are 

 in perfect condition and are exactly like those figured by Hansen (1912) for his specimen (Fig. 1 D-E). 



It would thus appear that specimens hitherto referred to this species fall into two definite groups : 

 (1) with the rostral plate serrulated along its anterior (and lateral) margins, the antero-lateral angles 

 produced into acute processes and with the outer margin of the antennal scale armed with only 



Fig. 1. Chalaraspidum alatum (W.-Suhm). A, ante- 

 rior end of immature female; B, right eye in dorsal 

 view; C, labrum; D, telson and left uropod in dorsal 

 view; E, telson in lateral view. All xo,. 



