j^ KCHINOIDKA. II. 



recoo'uize the value of affinities not based on the pedicellariie, since, of course, mih tlie accordance 

 in the structural characters of the test could induce lue to accept such geuera. To be sure, the Sfcreo- 

 cidaris ccDialiculata is not a \ ery txpical species of that jj^cuus, but tlie pedicellariae are of the struc- 

 ture peculiar to tliat 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 estabhshed the genus Cenfrocidaris 

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

 the broad bare space in the ambulacral and interambnlacral areas. This character is certainly a ver> 

 insufficient one for founding a genus on it, the more so as it is rather \ariable in canaliatlata. Pro- 

 fessor D(")derlein qiiite agrees with nie that the species canaliciilata has to be referred to Sfrreo- 

 cidaris^\ he rejects the genus Centrocidaris, and I think, likewise, that this genus cannot be niaiutaiued 

 as understood \^\ Professor Agassiz. Perhaps it can be maintained for the species C. /^oderleini, 

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

 test given b\- Professor Agassiz in the :Panamic Deep-Sea Echini. 



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

 cidaris elegaiis as another genus, Histocidaris, from Porotidaris p/irpiira/a, 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^, is sufficiently characteristic for such a generic separations (p. 24). It seems to me to 

 be verv easil)' 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 pedicellarife as the main 

 character: two-valved in Porocidaris, \hree-\i\\\<:d\\\ Histocidaris; the depressions iu the scrobicular areas 

 and the long neck of the radioles are also pointed out as characteristic of Porocidaris (p. 21 1 — un- 

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

 Professor Agassiz has in the least weakened these gromids for distinguishing Histocidaris from I'orn- 

 cidaris; Professor Doderleiu also accepts the genus Histocidaris. though he finds that the two 

 species einander nicht allzufern stehen (p. 98). 1 agree that it is too much to sa\ that 11. clcgans A\a.s, 

 no relation with [\ piirpurata, (p. 22), but I think the genus llisfocidans has to be maintained. — To 

 this genus will have to be referred Porocidaris Cobosi A. A<g.^ of which 1 have examined an authentic 

 specimen in the I'. S. National Museum, whereas Porocidaris .Millrri A. Ag., which 1 had likewise 

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

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

 Histocidaris: it is true that I lia\e seen the type-specimen in the Museum of Comparati\'e Zoolog\' 

 at Har\ard College, but since Professor Agassiz thought it right to forbid me to make aiu' studies 

 at the Museum, I could onh see it like any ordinarx \isilor. and nnldrlunatelv it was placed so high 

 that I could not see the pedicellaria'. F"rom the lack of a long neck on llie spines and of the de- 

 pressions iu the scrobicular areas I would conclude that il belongs to the genus /fistocidaris. What 1 

 have said of the species Dorocidaris niicans. based on specimens wrongh- referred to Porocidaris Sliar- 

 rcri, is right. I liope 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 inconsistenc\ in 



' I shall have to treat this species anrl the questions associated therewith more thorou<;hly in llu- Reports on tlie 

 I^chini of the German and the Swedish South-Polar Expeditions. 



' f>n p. 173 I have stated that this form of ijlobiferoiis ])e(licellriria- does not rcallv bcloiij; to llisloc. c/cgans. 



