142 DISCOVERY REPORTS 



with a pinnule arising from the epizygal, on the same side of the arm as the first pinnule, 

 comes next and thereafter the arm is normal. 



Dorsal pole. In four of the specimens from the South Sandwich Islands I could see 

 no dorsal pole ; it is very small and difficult to detect in the other specimens, large and 

 small, from the same locality. I failed to see a dorsal pole in one small specimen from 

 South Georgia and in one from the Bransfield Strait. It was present in all the other 

 specimens. 



Cirri. Fig. i a shows extreme types of cirri : in a^ and a-^ the segments are as short as 

 in any full-grown specimen I saw ; a^ and o^ are of cirri of very elongated segments, 

 though I have seen others slightly longer. The specimens from the South Sandwich 

 Islands and South Georgia have cirri of the first type though the segments are usually 

 a little longer than in the figure ; those of the South Sandwich specimens appear to be 

 the shorter. Two specimens from South Georgia, by no means the largest, have cirri 

 of the second, long, type. The specimens from the Bransfield Strait and the west coast 

 of Graham Land have cirri of the long type, though not usually so long as those 

 figured ; those from the latter locality appear to have the longer. All but two of twenty- 

 three Ross Sea specimens have cirri of the long type. In Fig. i a, i and 2 are from a 

 specimen from the South Sandwich Islands, 3 and 4 from one from the west coast of 

 Graham Land. 



Division series and lower brachials. None of the bigger specimens from South Georgia 

 have elongated axillaries and second brachials forming strong shoulders with the costals 

 and first brachials; in the biggest the shoulders are but slight. On the other hand, most 

 of the bigger specimens from the South Sandwich Islands and the Bransfield Strait and 

 all from the west coast of Graham Land have axillaries and second brachials which are 

 elongated and form strong shoulders with the costals and first brachials respectively. 

 Among the Ross Sea specimens there are none so large and old as in the collections from 

 the Falkland sector ; nevertheless, most of them have moderately long axillaries and 

 second brachials, but in only five do they form strong shoulders with the costals and 

 first brachials respectively. 



Ambulacral furrows on the disk. Mortensen (1918, p. 19) describes how variable is the 

 arrangement of the ambulacral furrows on the disk, "hardly two specimens (of his 

 collection) being alike"; Bernasconi {1932b, pp. 33-5, fig. 3a-e) gives a figure showing 

 the different arrangements in five specimens, though the differences are slight between 

 each of two pairs. Most of the specimens of the present large collection are well pre- 

 served with their arms bunched together so that the disk is hidden. But in ten from one 

 locality (St. MS 71) which are preserved otherwise the disk can be seen, and in each 

 one of them the arrangement of the ambulacral furrows is different from that in any 

 other ; in one it resembles that of two (a and b) in Bernasconi's figure. Mortensen writes : 

 "The normal condition evidently is that each primary ambulacral furrow divides so as 

 to provide four arms ; but often one or two of them (mostly the left posterior and the 

 right anterior) divide so as to proceed to six arms." In seven of my ten specimens the 

 left posterior divides so as to provide six arms, but the right anteriors are very variable. 



