I30 



ECHINOIDEA. I. 



nia\- be distingiiished by the pedicellariæ ; after tlie niaterial before me I must agree with Agassiz 

 that only two species can be distingiiished: iiiniiiillatits and trigonarins. Bnt tlien these two species 

 mav immediateh- be recognized \>\ their tridentate pedicellariæ (besides by the characters stated by 

 Agassiz |Rev. p. 427 seq.j). The tridentate pedicellariæ in Coloboc. atratus are very similar to those of 

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

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

 common form. The spicules are bihamate; in Hctcroccutrotiis the\- are exceedingly numerous as well 

 in tube feet as pedicellariæ, in Colobocentrotiis they are very few in number. 



Of the forms referred to Triplechmidæ?> we have still left Phyniosovia crcnulan- Ag., Iftiiii- 

 pedina cubcnsis Ag., and luirtihilis Dod. None of these forms I have been able to e.xaniine, so that 

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

 the e.xisting descriptions. Oi Pkyiiiosoiiin Agassiz figures valves of globiferous and tridentate pedicel- 

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

 pedicellariæ; 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 jRev. PI. \'II. 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 

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

 peculiar feature together with the crennlate 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 Les Phymosomiens , and readopts the name of Glyptocidaris^ by which it was originallv described 

 by Agassiz. I shall express no opinion whether it really is to be classed with Les Phymosomiens-), 

 partly because iny knowledge of these fos.sil forms is too small, partly becanse upon the whole I am 

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

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

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



Of llriiiiprdi)in ci<hcnsis 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 Trip/- 

 echinidcBK Agassiz says himself that it is a Pseudodiadematid, but to refer all Pscudodiadcinatidæ to 

 tTriplechinidæn is by no means admissible, so much the less as these :Triplechinidæ?' prove to be so 

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

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

 Cænopeditia 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 Les Pediniens is correct, but I mu.st regard it as certain that it has nothing to 

 do with . Triplcchiiiidæ . 



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

 grouping of the numerous genera. That the s)-stems mentioned above, which are chiefh- based on 

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



