ECHINOIDEA. I. 2I 



small pedicellarise are of a somewhat different form (PI. X, Fig. 26), and have a more or less powerful 

 end-tooth. Tridentate pedicellarice about as in Dorocidaris papilla ta, only with the edge somewhat 

 more dentate. Spicules of the common form. It is olnions that this species cannot) remain in the 

 genus Phyllacanthus as here limited, or be referred to an\ of the mentioned genera; it must form a 

 separate genus and retain the name of Chondrocidaris^ originally given to it by Agassiz'). 



The splendid Cidaris nirvafispiiiis described by Bell (74), is in its whole appearance so unlike 

 all other Cidarids that it is beforehand to be supposed that it represents a separate genus. The 

 examination of its pedicellarife also confirms this supposition. The globiferous pedicellarise (PI. VIII, 

 Fig. 37) have no end-tooth; the opening is large, reaching to the point, but its lower limit is remark- 

 ably irregular — the figured one is one of the most regular; sometimes there seems to be no definite 

 limit at all, the calcareous covering running out into irregular dents, as if it was broken off (which 

 is, howe\er, quite out of the question, as the pedicellaria was otherwise quite undamaged). The small 

 pedicellarise are of the same structure, the only difference being that the lower limit of the opening 

 is here often a rather regular transverse line. (The possibilit\- that the described and figured pedicel- 

 laria is really, in spite of its size, only the small form of the globiferous pedicellarise, is not excluded; 

 but on the only known specimen, which by the kindness of Prof. Bell I had the opportunity to 

 examine in British Museum, there seemed to be found no other kind of globiferous pedicellaria). The 

 tridentate pedicellaria; (PI. X, Fig. 9) are very peculiar, with some large, dentate crests of thin calcareous 

 lamellse longitudinalh' in the blade. No limb on the stalk. The spicules of the common form. For 

 this species I propose the generic name of Acanthocidaris. 



The ^^\\\\^ Porocidaris is established b)- Desor (op. cit. p. 46) for some fossil Cidarids, especially 

 distinguished bv a circle of pores in the scrobicular area; to this genus Wyvi He Thomson (394 — 95) 

 referred a Cidarid from . Porcupine under the name of Porocidaris purptirata. Whether it really 

 belongs to this genus cannot be decided, till the pedicellarife of the fossil species referred to it by 

 Desor, become known. But to judge by what is hitherto known the species may well seem to be a 

 Porocidaris^ and for the present there seems to be no reason to reject this commonly used name, and 

 P. purpiirata W. Th. may then be put down as the type of the genus. Peculiarities of this genus are 

 then the depressions in the scrobicular area (not pores as in the fossil species), the highly developed 

 neck of the spines, the highly serrate edge of the actinal radioles^). But the most particular feature 

 are the pedicellarise. Only one form is found which must be referred to the tridentate ones; they are 

 two-valved, highly compressed, and exceedingly large and conspicuou.s. The spicules of the 

 common form. 



To Porocidaris have later been referred the following species: P. rlegans Ag., Sharrcri Ag., 

 Miller i Ag., Cobosi Ag., gracilis Sladen, gracilis Doderl., misakiensis Yoshiwara, and incerta Koehler. 

 Of these species P. gracilis Sladen is, no doubt, only a young P. purpiirata, and this name is then to 

 be omitted as a synonym. P. clcgans (one of the type-specimens (<:Challenger St. 164a) examined in 

 British Museum): the tridentate pedicellarise are widely different from those of P. purpurata. There 



') List of Echinoderms sent to different Institutions in exchange for other specimens, with annotations. Bull. Mus. 

 Comp. Zool. I. 1863. 



2) Especially the latter fact is often mentioned as characteristic of the genus ; this, however, is not at all reliable, as 

 sufficiently shown by these researches. 



