54 ECHINOIDEA. I. 



coalesced, so that a series of large holes is found along the median line — and they may also be 

 found of the form, figured of A. coriacctivi). The pediceUarise (the tridentate ones) with short neck; 

 the stalk of the common structure. The tube feet in three series. The spicules (PL XI. Fig. 15) are 

 not so compact fenestrated plates as in A. fcnestralum^ the holes are much larger and fewer. In the 

 lower part of the tube foot the spicules are more narrow, at last only fine, thorny, irregular needles, 

 often a little widened as small fenestrated plates in one end or in both ends, or they have a larger hole 

 in the middle. Below they seem to be arranged in four longitudinal series, above the\- inclose the 

 whole foot as a close mail. The sucking disk well developed in the actiual tube feet. The primary 

 spines on the actiual side form a very conspicuous, regular series along the outer edge of the interambu- 

 lacral areas; in the ambulacral areas only 5 — 6 large spines are found scattered on the outer plates. 

 They are curved, and end in a little hoof. « Resembling more nearh' the primary spines of Phormosovio 

 than the characteristic flaring trumpet-shaped spines of Asthcnosoiiia , Agassiz says of these spines 

 (Chall. Ech. p. 88). As his nPJiormosoma* contains so widely different forms as Ph. placenta and Iiopla- 

 cantha this statement gives no clear information; the meaning of it is that they are similar to those 

 of A. fcncstrafiDii ; the hoof is little, short, and broad. 



Agassiz says of this species that it is rallied to Astlicnosoma gnibii in liaving an extremeh- 

 thick leathery cuticle (1. c); according to the informations given here there is no nearer relation 



between these two species. Agassiz further thinks tliat it is quite possible that this may l^e the 



adult of Asihniosoiiia fessclatiim . (1. c). After having examined the type specimen of this species I 

 can say with certainty that this is not the case; the two species are not even so very nearly related 

 even if they possibly belong to the same genus. — Tetradactylous pediceUarise ha\e not been found 

 in this species. The tridentate pediceUarise occur in two forms, between which there seem to be no 

 transitions. The large form is quite similar to the large tridentate pediceUarise in A. /nirsfrafiiiii 

 (PI. XIII. Fig. 5); the smaller form (PL XIII. Fig. 6, PL XIV. Fig. 15) is very peculiar, the blade deep, 

 filled by a rich net of meshes, and with a highly irregular edge witliout such large sinuations as are 

 found in A. fcnestratuin and coriaccitiii^ the widenings from the upper end of the apophysis continue 

 directly into tlic edge of the blade. When the pedicellaria is shut, tlie edges join complete!}.-, there is 

 only at the basal part a small open space. This form is a little more long-necked than usual. The 

 triphyllous pediceUarise are quite similar to those of A. fciicstratittii and coriacnii)i\ tlie stalk of the 

 pediceUarise of the common structure. Spicules and sucking disk as in A. fnicstrafitiir, the tube feet 

 in three series. All the primary spines on the actinal side are broken in the onl}- specimen known, 

 so that it is impossible to say anything of the form of the point; surely, howc\cr, they are not skin- 

 covered. — For the present it is impossible to decide whether this species is to be classed with A. 

 fcncstratum and coriaceum\ but several things speak in favour of this suppo.sition, and it will therefore 

 be most correct provisionally to refer this species to tlie genus Araosoma. Tlial llie membranous 

 interspaces between the plates are especially large in this species speaks, of course, only in fa\our of 

 the supposition that it really belongs to this genus. 



Among the sjjecimens ke]it in Pritish Museum under the name of AsHioiosoiiia Jiystrix, a piece 

 was found (from Barbados, 137 fathoms), which is no doubt a new species, and probabh- also belongs 

 to this genus. It is very similar to Calvcria hystrix, but is of a darker colour (brownish \iolet). 



