5° 



ECHINOIDEA. II. 



The triphyllous pedicellarise are likewise very similar to those of naresianus. The same holds good 

 for the spines and for the spicules of the tube-feet. — Agassiz states (Panamie Deep-Sea Echini p. 124) 

 that in young C. Wyvillii the labrum is followed by two plates, the sternum being absent; this is, 

 evidently, due to a lapsus memoriae. I need only refer to the figure 236 on p. 164 of the same work, 

 representing the plastron of a specimen i8 mm in length ; it shows the plastron to be of the same struc- 

 ture as in Urechinus. as might be expected to be the case. 



Perhaps two species have also been confounded under the name of Cystechinus Wyvillii in 

 the Challenger -Report. A comparison of the figures 1 — 4 with figs. 5 — 8 of PI. XXIX, further of 

 PI. XXIX. a with PI. XXIX. b at any rate gives a strong impression that two distinct species are re- 

 presented here; moreover, the high form is so very like Cystechinus Loveni that it must beforehand 

 seem much more reasonable to associate it with this species than with the low form of C. Wyvillii. 

 To be sure, Agassiz points out (Panamie Deep-Sea Ech. p. 159) several features which distinguish 

 C. Loveni from the high form of C. Wyvillii; but none of them seem to be of such value that it would 

 preclude regarding them as the same species. I have examined the pedicellarise of a specimen of the 

 high form (St. 147) and find them to agree with those of the low form of Wyvillii. On the other hand, 

 the pedicellarise of C. Loveni differ only little from those of Wyvillii ; I cannot therefore find herein 

 a definite proof that the high form is really the same species as the low form. Neither is it any proof 

 of their identity that they occur together on the same locality. The question can only be decided 

 after a very careful examination. 



« Cystechinus (Urechinus) Loveni (a specimen from the Albatross , St. 3415, examined in the 

 U. S. National Museum) differs only little from U.giganteus and Wyvillii with regard to the pedicellarise. 

 The globiferous pedicellarise are more like those of giganteus, though not so large; in the two speci- 

 mens I have found, there are two teeth on each side of the terminal opening of the blade. The tri- 

 dentate pedicellarise (PI. IX. Fig. 19) are upon the whole longer and more slender than in giganteus; 

 the edges of the basal part are generally more or less produced. Ophicephalous and triphyllous pedi- 

 cellarise as in giganteus. the latter, however, mostly a little more narrowed below the blade. Spines 

 and spicules do not present any characteristic specific features. 



The two species vesiea and Rathbuni originally referred to Cystechinus have with full right been 

 transferred by Agassiz to a new genus, Pilematechinus which is distinguished from the former f Ureelii- 

 nus) by the small size of the plates adjoining the peristome and especially through the structure of 

 the plastron, the labrum being in contact with the two plates 5. a. 2 and b. 2, a very conspicuous dif- 

 ference from Urechinus (Cystechinus) in which the plate 5. b. 2 ' alone occupies the whole space at the 

 outer end of the labrum. The genus Pilematechinus would thus represent a more primitive form than 

 Urechinus. Another very peculiar feature of this genus is the very thin and flexible test. 



Pilematechinus Rathbuni has been very carefully figured and described by Agassiz (Panamie 

 Deep-Sea Ech. p. 165) as regards the structure of the test; the pedicellarise etc. are not mentioned. 

 Having examined specimens of this species («Albatross St. 3360) in the U. S. National Museum I am 

 able to give some information thereof. The four usual kinds of pedicellarise were found. The globi- 



1 I quite agree with I.atnbert in his interpretation of this plate. (Comp. Lambert: Etudes morphologiques sur le 

 Plastron 'les Spatangides. Bull. Soc. Yonne. 1S92.1 



