214 



DISCOVERY REPORTS 



also is slightly larger. Further, there is a very conspicuous difference in the colour of 

 the secondary spines : a uniform yellowish or whitish with scarcely any indication of a 

 darker band in the West Indian form, brownish or with a very conspicuous brownish 

 band in the Ascension form. On the other hand, the young specimens from Annobon, 

 Gulf of Guinea, are much more like the Ascension form, the secondary spines being 

 almost as dark and the primary spines almost as distinctly verticillate as in the latter. 

 Also the dark band on the secondary spines may be rather distinct in the Annobon 

 specimens, and the dimensions of apical system and peristome are likewise rather alike. 

 It therefore seems to follow that the Ascension form is identical with the West African 

 form, viz. the var. africana of E. tribidoides. But as long as we do not know any large 

 specimens of either the typical tribuloides or the variety from Ascension (the largest of 

 the specimens in hand is 17 mm. h.d.), there is always the possibility that the Ascension 

 form does not grow to such a large size as the typical form and the var. africono, and if 

 so the Ascension form evidently should be regarded as a distinct variety. For the present 

 the question cannot be definitely settled. 



In regard to the pedicellariae, it may be pointed out that the large globiferous ones are 

 like those of the typical West Indian tribidoides. No tridentate pedicellariae are found 

 on any of the specimens examined. 



Measurements are given here of some of the specimens from Ascension and, for the 

 sake of comparison, of specimens from the West Indies and from Annobon of corre- 

 sponding sizes ; of the latter, unfortunately, only quite young specimens are available. 



h.d. 

 nun. 



IS 



13 

 10 



v.d. 

 mm. 



7-5 

 9 

 7 

 5 



Apical system 

 mm. 



Peristome 

 mm. 



Number of 



LA. 



Eucidaris tribuloides from Ascension 



Eucidaris tribuloides, West Indies, typical form 



7 (39 

 7 (41-2 

 6 (46-1 



4-5 (45 



) 



) 



7 (39 



8 (47 

 6-5 (50 

 5 (50 



) 



) 



Eucidaris tribuloides, var. africana from Annobon 



S-5 (50 

 4 (50 



) 



(54-5 

 (50 



) 



5 

 4-5 



A.proI.A. 



6-7 

 5-6 



Longest 



spines 



mm. 



II 



14 



7 



9 



20 



17 



19 



9 



8 

 9 



