ECHINOIDEA. I. 83 



the valve. The tridentate pedieellarire have rather strong- teeth in the point of the blade (PI. VII. 

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

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

 The neck rather long. The ophieephalons pedicellarise are of the common .structure resembling those 

 of Hypsiechinus\ they are short-necked. The triphyllous pedicellarise are very small, with finely serrate 

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

 beams to a compact reticulation, as in Hypsiechinus. 



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

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

 bihamate; the tube feet are remarkably broad at the base, corresponding to the uncommonly large 

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

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



From the Indian Ocean another species of Prionechinus has been described, Pr. Agassizii 

 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 pedicellarise or spicules; no figure is given. As 

 the original description of the genus Prionechinus, 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 forbesiana A. Ag. To the description of Agassiz I can add the following informa- 

 tions. The globiferous pedicellarise (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 pedicellarise (PI. VII. Fig. 22. 

 PL VIII. Fig. 33) resemble those of Prionechinus, 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 triphyllous pedicellarise (PI. VII. Fig. 26) resemble those of 

 Prionechinus, The stalks of the pedicellarise are of the same structure as in Prionechinus and Hypsi- 

 echinus, 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 Agassiz 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 fact is quite corresponding with regard to «Echinometridse and Triplechinida;:. Pom el 

 (324) refers this species to the genus Arbacina established by him. As the type of this species he 1 ) 

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

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

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



1) Revue des Echinodermes et de leur classification p. XLI. 1S69 (?). 



11* 



