j . ECHINOIDEA. II. 



classificatory value, natiirally led me to suppose that the same would generally be the case in all 

 Echinoidea. Later studies on other families of the Echinoids (Diadcmatidce, Temnopleuridce , the Irregu- 

 lar Echini) have shown that these structures are not always of so high a value in classification, and in 

 such groups the possibility of determination and classification of the fossil forms is, of course, more 

 favourable than in those groups, where the pedicellarise are of more importance, as in Echinidce, Toxo- 

 pneustidcr, Echinometridfr and, partly, Cidaridce. In these groups it is certainly not too much to say 

 that ('there cannot be any great certainty in the classification of the fossil formss. Regarding the 

 classification of the Irregular Echinoidea I have not said a word on that subject in Part I, and ac- 

 cordingly I have not condemned it either in passing or in a more thorough way. I have only sug- 

 gested that there would prove to be some uncertainty in the determinations of these forms, made with- 

 out the use of the microscopic characters afforded by pedicellarise etc. That I was quite right in that 

 suggestion is, I think, sufficiently proved in this second Part of my work. 



To turn now to the cases among the Cidaridcc pointed out by Professor Agassiz as especially 

 unfortunate results of my classificatory attempts. Such a case is the uniting of Cidaris metularia and 

 verticillata in one genus - ctwo species which are more readily distinguished by the characters of the 

 spines and tests than any other species of the family . That Cidaris baculosa is added to the same 

 genus is also held very unfortunate. It is true that Cidaris verticillata and metularia are very readily 

 distinguished by their spines as well as by their tests; the differences found in the spines, however, 

 could not convince me of the absurdity of uniting them in one genus, since I was unable to see very 

 reliable generic characters in the structures of the spines and certainly the differences between the 

 spines of C. verticillata and metularia are not more important than are those between C. -verticillata and 

 Phyllacanthus imperialis. which are united in one genus in the 'Revision of Echini-/. As for the differ- 

 ences in the structure of the test I might well have ascribed to them more systematic importance, if I 

 had been fortunate enough to have had a specimen of this C. verticillata at my disposal and had been able 

 to make a direct comparison. (It was upon the whole the lack of sufficient material for a comparative 

 study of the tests of the Cidarids which made me unable to judge of the real value of these structures 

 for the distinction of the genera.) Being then constrained to class the species after the structure of the 

 pedicellariae I could not get any other result than that these two species had to be regarded as not 

 too closely allied species of the same genus (p. 15), and since Professor Doderlein (Op. cit. p. 101) 

 after his very elaborate studies on the tests, the pedicellarise and spines of the Cidarids has now come 

 to the result that C. verlillata, bactdosa and metularia have to be placed in the same genus, only in 

 different subgeuera, I cannot think my result so very unnatural. 



That Cidaris a/finis is separated from Dorocidaris papillata. with which latter species it was 

 hitherto made synonymous, and even placed in another genus, Professor Agassiz finds erroneous. 

 There is nothing in the figures of the pedicellarise given by Mortensen to warrant such a transposi- 

 tion (p. 22). As evidence thereof the figures of pedicellarise of these two species given on PI. IX are 

 cited. That the figures of the tridentate pedicellarise as well as those of the small globiferous pedicel- 

 larise do not show so very important differences I willingly agree, but I have not used these differences 

 as distinguishing characters of the genera Dorocidaris and Cidaris. The main difference between 

 the two genera I find in the large globiferous pedicellarise; of the figures given thereof Professor 



