CO ECHINOIDEA. II. 



The triplnllons pedicellariæ are likewise ver\- siniilar to those of iiarrsiaiius. The same holds good 

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

 tliat in vonng C. Wyvillii the labrum is foUowed by two piates, the sternum being absent; this is, 

 evidenth-, due to a lapsus niemoriæ. I need ouly refer to the figure 236 on p. 164 of the same work, 

 representing the plastron of a specimen 18™'" in length; it shows the plastron to be of the same struc- 

 ture as in Urechinjis, as might be expected to be the case. 



Perhaps two species have also been confounded under the nanie of Cystccliiiins Wyvillii in 

 the Challenger -Report. A compari.son of the figures i — 4 with figs. 5 — 8 of PI. XXIX, further of 

 PL 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 Cysftchinns Lo^icni 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 (Panamic Deep-Sea Ech. p. 159) several features which distinguish 

 C.Lov/>ii from the high form of C.W\'viUii ; but none of them seem to be of such valne that it would 

 preclude regarding them as the same species. I have examined the pedicellariæ 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 hånd, 

 the pedicellariæ of C. Lovnti differ only little from those of Wyvillii ; I cannot therefore fmd herein 

 a definite proof that the high form is really the same species as the low form. Xeither is it an\- proof 

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

 after a very careful e.xamination. 



■iCystechinu.'; ■ (Urcchi)uis) Lovcni (a specimen from the Albatross , St. 3415, examined in the 

 U. S. National Museum) differs only little from U.gigantrus and Wyvillii \\\\.\\ regard to the pedicellariæ. 

 The globiferous pedicellariæ are more like those of gigantens, 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 pedicellariæ (PI. IX. Fig. 191 are upon the whole longer and more slender than \\\ gigaiitiiis ; 

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

 cellariæ as in gigant€7is. the latter, however, mostly a little more narrowed below the blade. Spines 

 and spicules do not present any characteristic specific features. 



The two .species vcsica and Rathbuni originally referred to Cysiecliiiuis have with full right been 

 transferred by Agassiz to a new genus, Pileinatechintis ^\\\c\\\^ å\st\ng\\isheåirom.t\\e^iorn\&r ( Ureclii- 

 niis) by the small size of the piates adjoining the peristome and especialh' through the structure of 

 the plastron, the labrum being in contact with the two piates 5. a. 2 and b. 2, a ver)' conspicuous dif- 

 ference from Urechiiius f Cysffcliiiiiisl in which the plate 5. b. 2 ' alone occupies the whole space at the 

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

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



Pilematechiiius Rathbuni lias been ver\- carefuUy figured and described \>\ Agassiz (Panamic 

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

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

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



■ I quite agree with Lambert in his interpretation of this plate. iConip. Lambert: Etndes morphologiques sur le 

 Plastron des Spatangides. Bull. Soc. Yonne. 1S92.) 



