ECHINOIDEA. I. 



127 



continuing some way into the blade as a distinct, a little serrate crest (PL XVII. Figs. 16, 20); tlie 

 form is otherwise somewhat varying, as the blade may be more or less widened in the onter part; tlie 

 larger ones have a rather powerfnl net of meshes, the small have almost none. The edge is rather 

 coarsely serrate in the lower part, finely serrate towards the point; there are no transverse series of 

 small teeth. A form as that figured by Agassiz (Rev. of Ech. PI. XXIV. 31), where, moreover, the 

 apophysis does not continue into the blade, I have not seen. Stewart (381) figures a valve of a 

 tridentate pedicellaria, and mentions this crest. In the same place he figures a valve of an ophice- 

 phalous pedicellaria to whicli I may refer; they are dentate in the edge to an uncommonly high 

 degree, although some difference is fonnd in this respect, but I have not seen them with so smooth 

 edges as in the figure by Agassiz (loc. cit. Fig. 32). The ophicephalons pedicellariæ have almost no 

 neck, as has already been observed by Stewart. The stalk, which is, like those of the other jDedicel- 

 lariæ, thick and compact, has a little constriction above. The triphylloiis pedicellariæ are nncommonh- 

 lengthened (PI. XVII. Fig. 4) withorit teeth in the edge. What Stewart has taken to be triphylloiis 

 pedicellariæ (he does not figure them), I think to have been quite small, tridentate pedicellariæ. The 

 great variation in the size of these (the tridentate) pedicellariæ, and the broad, spoon-shaped character 

 of their jaws make the smaller forms closely resemble the trifoliate variety and lend weight to Prof. 

 Agassiz's view, that the latter are rarely (sic! — early) stages of the former (381. p. 911). That there 

 can be no question of this need not be more nearh' explained here, a reference to the informa- 

 tions given above with regard to the development of the pedicellariæ, will be sufficient. The spicules 

 of the tube feet are very peculiar; aloug one side of the tube foot is found a series of large spicules 

 formed as long, fenestrated, thoru}- tubes; they are parallel to the longitudinal axis of the foot, and 

 are placed in such a way, that the upper end is projecting, while the lower end is covered by the 

 spicule following below. Towards the sucking disk the spicules become smaller, at last onh' flat, length- 

 ened fenestrated piates. ()n the opposite side of the tube foot is often — but not always — found 

 an irregular series of much smaller spicules more or less perforated. Stewart') has given figures of 

 these spicules, to which the reader is referred ; I have never, however, seen the large spicules branched, 

 as they are figured here, Stewart does uot know in which species it is that he has found these 

 remarkable spicules ; later (381) it has become clear to him that it is Stonopneiistes variolaris. — Whether 

 Stoiiiopii. afropitrpnrca Woods (447) is a separate species, or, as Ramsay (311. p. 11) thiuks, only a 

 variety of variolaris^ I cannot tell with any certainty, as I have uot seen this form, and the descriptiou 

 gives no information of pedicellariæ and .sjjicules. These structures must be examiued, before the 

 question can be definitively decided. 



Parasalcnia gratiosa Ag. I can only give little information of this very characteristic form 

 beyond what has been stated b}- Agassiz, Liitken, and Stewart. A primary tubercle is found on 

 all the ambulacral piates; the buccal membrane contains numerous, ratlier large, fine fenestrated piates, 

 of which only a few are complicate and carry pedicellariæ. No sjjines on the buccal piates. The 

 globiferous pedicellariæ have a tubular blade, without lateral teeth. No neck; glands seem to be found 

 on the stalk, which is compact. The tridentate pedicellariæ are long and very narrow, finely serrate 

 in the edge; they remind very much of those in Paracci/ frotus lividjis^ but the serrations are finer. 



') On the Spicula of the regular Echiiioidea. Transact. Linn. Soc. XXV. PI. I,, fig. i. 1S65. 



