J. ECHINOIDEA. II. 



classificatorv value, naturalh led me to suppose that the same would i^enerally be the case in all 

 Echinoidea. Later studies on other families of the Echinoids {DiademaHd(e. Tevtnopleuridce . the Irregu- 

 lar Echini I ha\e 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 pedicellariae are of more unportance, as in Echinidce. Toxo- 

 pneusHda, Echinometrida and, parth, Cidaridce. In these groups it is certainh not too much to say 

 that there cannot be an\ great certaiut\ in the classification of the fossil forms^. — Regarding the 

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

 cordingh- I have not condenmed it either in passing or in a more thorough way. I ha\e onl\- 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 b\- pedicellaria; etc. That I was quite right in that 

 suggestion is, 1 think, sufficientl\ pro\ed in this second Part of nn work. 



To turn now to the cases among the Cidnridcf pointed out b\ Professor Agassiz as especialh' 

 unfortunate results of nn classificatory attempts. Such a case is the uniting of Cidarix victularin and 

 vcrticillata in one genus — two species which are more readily distinguished by the characters of the 

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

 genus is also held \er\ unfortunate. It is true that Cidaris verticillata and mchtlaria are ver\- readily 

 distinguished b\ their spines as well as by their tests; the differences found in the spine.s, however, 

 could not convince me of the absurdity of luiiting 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 mctvlaria are not more important than are those between C. verticillata and 

 Phyllacaiillius ivipirialis. 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 m\- disposal and had been able 

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

 stud\' 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 

 pedicellarise I could not get an\ 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 Dciderlein (Op. cit. p. loi) 

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

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

 different subgenera, 1 cannot think m\' result so ver\ unnatural. 



'I'lial Cidaris a/finis is separated from Dorucidnris papillafa. with which latter species it was 

 hitlierl(j nuide syuonynujus, and o\en placed in another genus, Profes.sor 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- 

 laria.' do not show so very important differences I willingh agree, hut I lui\e not used these differences 

 as distinguishing characters of the genera Dorocidaris and Cidaris. Tlie nuiin difference between 

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



