1 3 o 



ECHINOIDEA. I. 



may be distinguished by the pedicellarise ; after the material before me I must agree with Agassi z 

 that only two species can be distinguished: main Hiatus and trigonarius. But then these two species 

 may immediately be recognized by their tridentate pedicellarise (besides by the characters stated by 

 Agassiz [Rev. p. 427 seq.]). The tridentate pedicellariae in Coloboc. atratus are very similar to those of 

 //. trigonarius; the valves join through their whole length (PI. XIX. Fig. i); in C. Mcrtensii I have 

 not succeeded in finding these pedicellarise. The ophicephalous and triphyllous pedicellariae of the 

 common form. The spicules are bihamate; in Heteroccntrotus they are exceedingly numerous as well 

 in tube feet as pedicellariae, iu Colobocentrotus they are very few in number. 



Of the forms referred to < Triplechinida-* we have still left Phymosoina crcnularc Ag., Hcmi- 

 pedina cubcnsis Ag., and mirabilis Dod. None of these forms I have been able to examine, so that 

 their place must for the present remain undecided. We may, however, draw same conclusions from 

 the existing descriptions. Of Phymosoma Agassiz figures valves of globiferous and tridentate pedicel- 

 lariae (Rev. of Ech. PI. XXV. 4, 5) from which is seen that no lateral teeth are found on the globiferous 

 pedicellarise; whether a neck is found or not is not mentioned. The spicules are not known. A peculiar 

 feature is seen from the figures given by Agassiz (Rev. PI. VII. a. f. 6, 8, 9), viz. that the pores form 

 arcs with alternately two and three pairs. As the figures cited are photographs, there can be no 

 doubt of their correctness, although Agassiz, as far as I can see, does not mention this fact. This 

 peculiar feature together with the crenulate tubercles renders it undoubtful that this form has 

 nothing to do with the genuine Kchinids. Pomel (324) puts it down as the only recent representative 

 of L,es Phymosomiens, and readopts the name of Glyptocidaris , by which it was originally described 

 by Agassiz. I shall express no opinion whether it really is to be classed with <>Les Phymosomieiis , 

 partly because my knowledge of these fossil forms is too small, partly because upon the whole I am 

 rather sceptical with regard to the possibility of referring with certainty the recent forms to the fossil 

 ones. Accordingly I agree with Pom el "that the name of Glyptocidaris must be readopted for this 

 form, as the name of Phymosoma has originally been used of fossil forms. 



Of Hemipcdina cubcnsis Ag. are figured (Rev. of Ech. PI. III. f. 6 7) a tridentate pedicellaria 

 and a smaller one which is stated to be a young tridentate pedicellaria, but which is rather a globi- 

 ferous or ophicephalous one; neither is given with sufficient details. The spicules are not known. 

 The perforated tubercles show, however, that this form has nothing to do at all with the other .< Tripl- 

 echinid(Bi>. Agassiz says himself that it is a Pseudodiadematid, but to refer all Pscudodiadcinatid(Z to 

 Triplcchinid(B is by no means admissible, so much the less as these ^.Triplechinidce^ prove to be so 

 heterogeneous that the genera referred thither must be distributed to three different families. Pomel 

 (324) refers it to L,es Pediniens as the only recent representative, and he readopts the name of 

 C&nopedina by which Agassiz has originally described it. With regard to the name I must agree 

 with Pomel for the same reasons as stated above under Glyptocidaris crenularis. I shall not contest 

 that the referring to L,es Pediniens* is correct, but I must regard it as certain that it has nothing to 

 do with .Triplcchinid(z. 



Having thus given a natural grouping of the species I shall have to treat the question of the 

 grouping of the numerous genera. That the systems mentioned above, which are chiefly based on 

 the number of the pairs of pores, give no impression of the real relation of the forms need not to be 



