446 BULLETIN 82, UNITED STATES NATIONAL MUSEUM VOLUME 1 



form, each with its tuft of dorsal spines. The arrangement of the syzygies and the struc- 

 ture of the proximal pinnules is not the same in these two species, which are sharply 

 separated from each other by the fact that the apex of the centrodorsal is bare in P. 

 joubini, while it bears cirri in P. kerguelensis. 



He says further that the cirri of P. joubini are quite comparable to those of P. 

 vanhoffenianus; in both species they show at the base three or four short segments 

 while those following are elongated. 



The value of the presence or absence of the ambulacral skeleton as a differential 

 specific character has already been discussed. The axillaries of P. joubini are not in 

 any way different from some of the axillaries in the more developed of the 

 two Discovery specimens figured by Bell. The first brachials are also the same as in 

 this specimen. The occurrence upon the brachials of a tuft of dorsal spines merely 

 indicates that this characteristic feature of the young has not as yet been suppressed. 

 The extent of the bare dorsal pole of the centrodorsal is a very variable feature and, 

 so far as I have been able to determine, offers no grounds for systematic differentiation. 

 The structure of the earlier pinnules as described by Vaney indicates merely the imma- 

 turity of the specimen; in all of the Heliometrinae the earlier pinnules in the relative 

 proportions of their component segments as well as in their interrelationships vary 

 greatly with age and relative maturity. The cirri of Vaney's specimen agree with 

 those of P. vanhoffenianus, as opposed to P. kerguelensis, this again merely indicating 

 immaturity; but like the lower pinnules the cirri of the Heliometrinae are of little 

 systematic value. 



I cannot see that Promachocrinus joubini differs in any essential particular from 

 P. kerguelensis, of which species it appears to be a specimen which has not yet attained 

 its full development. It can be matched in all its features by specimens taken by the 

 Challenger at Kerguelen, as well as by others taken by the Discovery at her winter 

 quarters. 



These conclusions were fully borne out by the work of Dr. Dilwyn John on the 

 crinoids of the Discovery Investigations (1938). As he remarked in his Belgica report 

 (1937), the range of variation of P. kerguelensis is even greater than it need be to embrace 

 vanhoffenianus and joubini. However, it appears from his investigations that certain 

 characters, such as the proportions of the cirrus segments and brachials and the occur- 

 rence of side plates in the pinnules, are correlated not so much with age as with the 

 locality, specimens from high and low latitudes having a distinct tendency for varia- 

 tion in one direction or another. 



History. Writing from on board the Challenger, Dr. R. von Willemoes-Suhm in 

 a letter to Professor von Siebold published by the latter in 1874 said that at Kerguelen 

 a Gomatula, which he did not further particularize, was characteristic of the second 

 littoral zone in from 73 to 219 meters. 



Dr. P. H. Carpenter in 1879 mentioned this species under the name of Promacho- 

 crinus kerguelensis, in that year (twice), in 1880 (twice), in 1883 and in 1884 calling 

 attention to various morphological features exhibited by it, finally describing it in 

 detail and figuring it in 1888. 



Perrier in 1886, quoting some of Carpenter's statements regarding the anatomy, 

 emended the specific name to "kerguelenensis" and "kerguellenensis," the former being 

 adopted by Bell hi 1908. 



