i-;eiiiN()U)i;A. ii. j, 



nothiirid(C and ficliiiionniridce, or better still, to read the chapter on the classification of tlie Diadein- 

 atids in in\ paper on the Siam-Echinoidea (pp. 4(j— 56) will recognize that niv classification is not 

 based on the pedicellarijc alone. It is trne that my classification of the Cidaridfr is almost exclusively 

 based upon the structure of the pedicellaria- ; but that is due to my inability to find other characters 

 which could be used with success. Any reader of ni\ introductor\ remarks on the FauiilN Cidaridu- 

 will recognize that I ha\e not omitted to take other characters into consideration, while the conclusion 

 of that cha])ter is as follows (j). 31 1 : When in the diagnoses of genera given here other features than 

 pedicellariae and spicules have onl\- been mentioned exceptionalh the opinion of coiuse is not that 

 these structures should be sufficient for definitive diagnoses. It has already been emphasized above, 

 and I shall here empha.size once more that all these .structures nuist be thoroughly examined in order 

 to get the mutual relations of the forms established. That I ha\e here onl\- treated the pedicellarise 

 more thoroughly is a consequence of the fact that neither m\ material nor my lime has permitted 

 me to treat the other features luore particularly. The systeiu of the Cidarids cannot get its definitive 

 formulation, until all features ha\'e been e.xauiiued in a greater number of species lor best in all 

 species). What is given here is a provisional classification, which can scarcely be correct throughout... 

 — Whilst I must thus decidedly protest against the accusation of having based m\- classification on a 

 single character, I beg to suggest to Professor Agassiz whether that would not suit the classification 

 oi\h.^ 'Echinoinctridce asiA Echi7tidcc . given in the Revision of Echini . These Families are founded 

 exclusively on the number of pores in the ambulacral plates, all the genera with only three pairs of 

 pores being included in the family Ecliimdtc those with more than three pairs of pores in the family 

 Echinometrid(r. And as for the impossible associations resulting from such artificial divisions according 

 to one character I might suggest to Professor Agassiz whether the placing of Heiinprdina. Phynio- 

 soma, Ec/i/ints. Toxopneiistes. Tripneustcs and Etcc/id/hs ( Hcliocidarisi in one subfamih', Triplrcliiiiidcf. 

 as is done in the Revision , does not deserve to be thus characterized. 



Professor Agassiz speaks in a \er\ depreciator\nianner of the results of my classification, whicli 

 «ciilminate in such impossible associations that we are loath to follow his lead . It would have been 

 very interesting to hear some instances of these impossible associations, but unfortunately Profes.sor 

 Agassiz confines his examples to a few Cidarids. It scarcely seems fair to condemn the whole of my 

 results on the evidence of a few debatable cases among the Cidarid(r. the classification of which 

 family is expressh- stated to be pureh provisional. I should like to learn what are the impossible 

 associations in my classification of the Ec/tmofh/irida-, Echinoiiirtrida- and the Echinidcc. the more so, 

 since it was the greater naturalness of the associations resulting from my classification which were 

 to my mind a proof of its correctness. I will, however, leave it to others to compare m\- arrangement 

 of the forms included in, let us sav. the genus Siroiigylocoifrotns nx in the ¥am\\\ Ec/nnomt'frid(F -with 

 the arrangement given in the ;< Revision of Echini . And upon the whole 1 \enture to believe that, 

 .since Professor Doderlein has now accepted my classification of these groups in the main points, it 

 will be agreed, at least, that it cannot be so ver\- unnatural; otherwise, so careful and judicious a natu- 

 ralist, with so profound a knowledge of the whole class, would certainly not have accepted it. 



Regarding the use of pedicellariic in the definition of systematical characters of Echini Profes.sor 

 Agassiz agrees that it uui> be desirable to employ all the data possible from whatever .source. 



