438 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VULU.ME 1 



Side plates and spicules. — Dr. Dilwyn John made a particular study of the abun- 

 dant material collected by the Discovery Investigations with regard to this character, 

 from which he concluded that the occurrence of well-developed side plates is not a sign 

 of immaturity but can be correlated with the locality. In 37 specimens from the Brans- 

 field Strait area he found that 29 have both plates and spicules and two more have 

 plates alone, whereas out of 34 from South Georgia only 5 have plates and none have 

 both plates and spicules. He also \\Tites that it is not only a question of numbers, 

 the degree of plating varies as well. Of the 29 specimens from the Bransfield Strait 

 area at least 13 are heavily plated, while the plates in the five from South Georgia are 

 very small. It appears from this, that in this sector of the Antarctic, the specimens of 

 P. kergueleiisis living in lower latitudes are most often without plates and always devoid 

 of spicules and that the majority of those living in high latitudes have big plates along 

 the entire lengths of the pinnules and many spicules in the tentacles. Those living 

 intermediately seem to be intermediate in character. In support of this, Grieg de- 

 scribed the pinnules of seven specimens from the Bransfield Strait as having well- 

 developed covering plates. However, Mortensen (1918) found no plates in 16 specimens 

 from the east side of Graham Land as well as in four from South Georgia. 



Dr. John also examined 38 specimens from the Ross Sea. Thirteen have plates 

 along the ambulacra and spicules in the tentacles; in eight the plates are strongly de- 

 veloped, in five they are small and scattered. Another thirteen have small and scattered 

 plates but no spicules. One specimen has spicules in the tentacles but no plates, and 

 eleven liave neither plates nor spicules. Two pinnules of a small Challenger specimen 

 from Kerguelen were examined; one has a single diminutive plate near the tip, the other 

 has none. 



However, among the twenty B.A.N.Z.A.R.E. specimens from Kerguelen, Dr. John 

 found tliat some of the larger ones have strong side plates along the distal halves of the 

 distal pinnules. In other specimens they are lacking. None appeared to have spicules 

 in the tentacles. 



Variations in the cirri, division series and lower brachials. — In the Discovery In- 

 vestigations material Dr. John found that the specimens from the South Sandwich 

 Islands and South Georgia usually have cirri with relatively short segments, whereas 

 specuncns from Bransfield Strait and the west coast of Graham Land have cirri with 

 longer segments. Also out of 23 specimens from the Ross Sea, 21 have cirri of the long 

 type. 



As for the arm ossicles, none of tlie bigger specmiens from South Georgia have 

 elongated axillaries and second brachials forming strong shoulders with the IBri and 

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

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

 all those from the west coast of Graham Land have axiUaries and second brachials which 

 are elongated and form strong shoulders with the IBr, and first brachials respectively. 

 .\mong tlie Ross Sea specimens there are none so large and old as in the collections 

 from the Falkland sector; however, most of them liavo moderately long axillaries and 

 second bracliials but in only five do they form strong shoulders with the IBri and first 

 brachials. 



Ambulacral jurrows on the disk. — -It is obvious from all accounts that these are 

 extremely variable. Bernasconi (1932) figures the disks of five specimens, all more or 



