i64 DISCOVERY REPORTS 



H. microplax Fisher, Mindanao Sea; H. arcystata Fisher, Philippines; //. polyacantha 

 and H. clarki Fisher, Pacific coast of North America. 



In the absence of a series of//. co?npacta it is not possible to determine what may con- 

 stitute the real diff'erences which separate it from studeri, for there is no reason to expect 

 that compacta is less variable than other species. 



I believe we can safely conclude at this time, that studeri and compacta are " divisions " 

 of a wide-ranging subantarctic multispinous stock (as distinguished from the simplex- 

 pagenstecheri stock). So far as there are species in Henricia these widely separated 

 "colonies" can conveniently be called species. But the task of putting into words 

 exactly what characters distinguish each is vastly complicated by the wide range of 

 parallel variations which each species reveals as soon as sufficient specimens are 

 assembled. Perhaps we shall never agree on specific limits in Henricia for the simple 

 reason that Linnaean species probably do not exist. 



Where studeri and obesa range together, as at St. WS 86, a few specimens may reason- 

 ably be regarded as intergrades. They are intermediate in what are assumed to be 

 specific characters and are intergrades in the sense that they are probably hybrids. An 

 exactly similar situation exists in the north Pacific whenever independent stocks of 

 Henricia overlap in their ranges. 



Studeri may be distinguished from obesa by the smaller skeletal intervals between the 

 abactinal primary plates and the typically more numerous and slightly larger delicate 

 spinelets of these plates. The adambulacral plates frequently have 2 spinelets deep in 

 furrow and 12-16 subambulacral spines, of which three commonly stand on the furrow 

 margin. There is less interval between successive plates in studeri. The plates of actinal 

 surface are more densely spined and have smaller skeletal intervals. The series of actinal 

 plates in specimens of approximately equal size extends farther along the ray in studeri, 

 sometimes to the tip, whereas in obesa this series adjacent to the adambulacrals usually 

 dies out at the middle of ray. This is a useful guide character for doubtful specimens but 

 must be used in connection with the sum of other diagnostic features. 



The general appearance of most of the specimens from St. WS 86 is closely similar to 

 that of H. microplax, 200 fathoms, Mindanao Sea (Fisher, 1919, pi. 120, figs. 3, 5; 

 pi. 121, fig. 2). 



A colour note attached to a specimen from St. WS 81 reads " Orange yellow to light 

 red dorsally, dull yellow ventrally". 



Type locality. South of Cape Horn, 99 m. 



Distribution. Cape Horn — Falkland plateau, 74-341 m. 



Henricia obesa (Sladen) 



(Plate XI, fig. 2) 



Cribrella obesa Sladen, 1889, p. 544, pi. 96, figs, 3, 4; pi. 98, figs. 5, 6. 



Cribrella hyadesi Ferrier, 1891, p. 100, pi. 9, figs, la-id. — Leipoldt, 1895, p. 578, pars. — Meissner, 



1896, p. 99. - 



Cribrella pagensiecheri Meissner, 1904, p. 13. — Ludwig, 1905, p. 68. 



