SOME WEST INDIAN ECHINOIDS. 



13 



is a distinct species, but also another distinct new species (C. rugosa) is found here, 

 which has hitherto been confounded with 0. cixlaris, whereas the true C. cidaris 

 (D. papillata) does not seem to occur in the West Indian seas at all. Tliis r&sults 

 in a much more restricteil distribution of C. cidaris, which accordinglj' occurs oidy 

 in the Eastern Atlantic and the Mediterranean. The Challenger specimens from 

 St. Paul's Rocks which I have maintained to be true C. cidaris (Ingolf Echinoidea, 

 pt. 1, p. 170), Clark supposes also to belong to C. rugosa. After the separation 

 of C. rugosa from C. cidaris I do not venture to maintain that the St. Paul's 

 Rocks specimens belong to the latter species, as I have not examined the structure 

 of the test in detail; the pedicellarife are not sufficiently characteristic in the 

 dilferent species to permit a definite answer to this c[uestion. C. cidaris would thus 

 form one more species peculiar to the eastern Atlantic deep sea (besides Poriocidaris 

 purpuraia and Sperosoma grimaUii) a fact tending considerably to strengthen my 

 view that this part of the Atlantic deep sea area forms a separate region. (See 

 Ingolf Echinoidea, pt. 2, p. 187.) 



Having recently obtained some additional material of C. abyssicola and also a 

 specimen of C. rugosa, I have taken the occasion to compare these forms carefully 

 with C. cidaris and to form an opinion of the question of their specific value. 

 The result of my investigation is that I think rugosa is a distinct species, though I 

 cannot agree with Clark regarding all the characters wliich he gives as distinguisliing 

 it from C. cidaris. That C. abyssicola is a distinct species also seems to me beyond 

 doubt; but I tliink it necessary further to distinguish as at least a distinct variety 

 a form with slender radioles liitherto confounded with C. abyssicola. Whether it 

 will perhaps ultimately prove to be a species distinct from abyssicola I am unable 

 to ascertain from the material at my disposal. A more detailed comparison of the 

 two forms of C. abyssicola will thus be necessary. Also a few remarks on C. rugosa 

 may not be out of place. 



CIDARIS ABYSSICOLA, var. TERETISPINA, new variety. 



Plate 7, figs. 1-2; plates 8-10; plate 14, figs. 2-4; plate 15, figs. 3-0, 9-11; plate IG, fig. 11; plate 17, 



figs. 2-3, 5, 9-11. 



Measurements of the Typical Form. 



Measurements of var. terelispina. 



