ECHINOIDEA. I. 83 



the valve. The tridentate pedicellariæ have rather strono; teeth in the point of the blade (PL VII. 

 Fig. 21); along the median hne of the blade the holes are large, lengthened; no net of meslies in the 

 bottom. Only the points of the valves join when the pedicellaria is shnt; below they are wide apart. 

 The neck rather long. The ophicephalous pedicellariæ are of the common strnctnre resembling those 

 of Hypsiechiuits\ they are short-necked. The triphyllons pedicellariæ are very small, with finely serrate 

 edge (PI. VII. Fig. 25). The stalk of the pedicellariæ consists of longitudinal fibres connected by cross- 

 beams to a compact reticulation, as in Hypsiccliiiius. 



That the specimen from st. 207 is no Prioi/cchiiius has been stated above ; unfortunately it is 

 impossible to decide with certainty what it is, as all the pedicellariæ are wanting. The spicules are 

 bihaniate; the tube feet are remarkabh' broad at the base, corresponding to the uncommonly large 

 pores. The spines are of the same structure as in Prioiiechinus. As no sufficient characters can be 

 given of this form, I shall give it no name, but only separate it from Pnoncchinus. 



From the Indian Ocean another species of Prioncchhms has been described, Pr. Agasstzn 

 Wood-Mason & Alock (441); whether it really belongs to the genus Prionechinus cannot bee seen from 

 the description, and no informations are given of the pedicellariæ or spicules; no figure is given. As 

 the original description of the genus Pn'oicc/iiiiiis, as here shown, is anything but good and faultless, 

 the referring to this genus must be considered uncertain, until a closer examination has been made 

 with regard to the characters pointed out here. 



Cottaldia forbcsiaiia A. Ag. To the description ofAgassiz I can add the following informa- 

 tions. The globiferous pedicellariæ (PI. VII. Fig. 32), like those oi Prionechinus.^ have only one, unpaired 

 lateral tooth, and the edges of the blade are thickened, but not connected by cross-beams; the basal 

 part is somewhat more rounded than in Prionechinus. The tridentate pedicellariæ (PI. VII. Fig. 22. 

 PI. VIII. Fig. 33) resemble those of Priotiechinus^ but have only small teeth in the point of the blade. 

 The valves join only with the points, and are wide apart below, when the pedicellaria is shut. The 

 neck very short. The ophicephalous and triphyllons pedicellariæ (PI. VII. Fig. 26) resemble those of 

 Prio7iechinus. The stalks of the pedicellariæ are of the same structure as in Prioncchiniis and Hypsi- 

 cchinus, only a little more dense. The spicules, as shown by Bell (50), are bihamate. The spines are 

 thicker and not so sharply serrate as in Hypsiechimis , but the point is constructed as in the latter, 

 only more rounded. — Whether this species really belongs to the genus Cottaldia., which has been 

 established by Desor for some small fossil Echinids, must be regarded as very doubtful, as has also 

 been observed by A g a s s i z himself. Upon the whole the referring of recent forms to genera established 

 for fossil ones, is exceedingly problematic, if the tests do not show particularly characteristic features. 

 It has even proved impossible to classify the recent species correctly after the tests and spines only, 

 as has been shown above with regard to the Cidarids and Echinothurids, and it will be shown below 

 that the faet is quite corresponding with regard to Echinometridæ > and «Triplechinidæ>. Pomel 

 (324) refers this species to the genus Arbaciiia established by him. As the type of this species he ■) 

 gives Arbacia mon il is (Ag.) that is to say, a fossil form, and here the same observation holds good as 

 with regard to Cottaldia: we cannot pro ve at all that the recent form is the same genus, as we want 

 the most important characters. It nnist be admitted, however, that A. forbesiana shows really a great 



■) Revue des Échinodermes et de levir classification p. XLI. 1869 (?). 



II* 



