10 ECHINOIDEA. II. 



recognize the value of affinities not based on the pedicellarise, since, of course, only the accordance 

 in the structural characters of the test could induce me to accept such genera. To be sure, the Sfereo- 

 cidaris canaliculata is not a very typical species of that genus, but the pedicellarise are of the struc- 

 ture peculiar to that genus, and I did not find sufficient charaters in the structure of the test for 

 founding a separate genus on it. Now, Professor Agassiz has established the genus Centrocidnris 

 for this species and the species Goniocidaris; DiJdcrleini A. Ag., the only character of the genus being 

 the broad bare space in the ambulacral and interambulacral areas. This character is certainly a very 

 insufficient one for founding a genus on it, the more so as it is rather variable in canaliculata. Pro- 

 fessor Doderlein quite agrees with me that the species canaliculata has to be referred to Sterro- 

 cid(iris l \ he rejects the genus Centrocidaris, and I think, likewise, that this genus cannot be maintained 

 as understood by Professor Agassiz. Perhaps it can be maintained for the species C. Dodcrl/'un, 

 which had to be left incertse sedis by Professor Doderlein, in spite of the careful description of the 

 test given by Professor Agassiz in the Panamic Deep-Sea Echini. 



Professor Agassiz further finds it impossible to conceive the ground for my separating Poro- 

 cidaris elegans as another genus, Histocidaris, from Porocidaris purpurata, < unless it be that the cha- 

 racters of a single valve of a small globiferous pedicellaria, which he (I) figure(s) as perhaps belonging 

 to that species 2 , is sufficiently characteristic for such a generic separations (p. 24). It seems to me to 

 be very easily seen from my remarks on Porocidaris (p. 21 22) and the diagnoses of the genera Histo- 

 cidaris and Porocidaris (p. 30), that I regard the differences in the tridentate pedicellarise as the main 

 character: two-valved in Porocidaris, three- valved in Histocidaris; the depressions in the scrobicular areas 

 and the long neck of the radicles are also pointed out as characteristic of Porocidaris (p. 21) -- un- 

 fortunately, the two latter characters have not been mentioned in the diagnosis. I do not see that 

 Professor Agassiz has in the least weakened these grounds for distinguishing Histocidaris from Poro- 

 cidaris; Professor Doderlein also accepts the genus Histocidaris, though he finds that the two 

 species ^einander nicht allzufern stehen = (p. 98). I agree that it is too much to say that H. elegans has 

 no relation with P. purpurata . (p. 22), but I think the genus Histocidaris has to be maintained. - - To 

 this genus will have to be referred Porocidaris < Cobosi A. Ag., of which I have examined an authentic 

 specimen in the U. S. National Museum, whereas ^Porocidaris ; Miller i A. Ag., which I had likewise 

 the opportunity of examining there, is a Stereocidaris. probably nearly related to Stereocidaris japonica 

 Doderlein. As regards Porocidaris Sharreri it still remains uncertain, whether it is a Porocidaris or a 

 Histocidaris; it is true that I have seen the type-specimen in the Museum of Comparative Zoology 

 at Harvard College, but since Professor Agassiz thought it right to forbid me to make any studies 

 at the Museum, I could only see it like any ordinary visitor, and unfortunately it was placed so high 

 that I could not see the pedicellarise. From the lack of a long neck on the spines and of the de- 

 pressions in the scrobicular areas I would conclude that it belongs to the genus Histocidaris. What I 

 have said of the species Dorocidaris micans, based on specimens wrongly referred to Porocidaris Shar- 

 ren\ is right. I hope to be able soon to give a more detailed description of this species. On the 

 other hand, I must agree that Professor Agassiz is right when reproaching me with inconsistency in 



1 I shall have to treat this species and the questions associated therewith more thoroughly in the Reports on the 

 Kchini of the German and the Swedish South-Polar Expeditions. 



2 On p. 173 I have stated that this form of globiferous pedicellaria' does not really belong to Histoc. elegans. 



