ECHINOIDEA. I. 49 



Another very distincth- marked group is formed by the species Asf/iniosoiiia variuvi Grube, 

 Gnibci Agass., iircns Sarasin, and Iictcracfis Bedford, all which species I have had occasion to 

 examine. The primary spines 011 the actinal side are curved, and end with a thin, but rather long, 

 little conspicuous hoof; they are green with dark rings. All the spines on the abactinal side and the 

 secondary ones on the actinal side are covered with skin; on the larger spines the bag of skin is 

 repeatedh- constricted (Chall. Ech. PI. XVI), on the small spines there is onl\- a simple bag of skin at 

 the point (poison apparatus — Sarasin 350, 352); these skin-covered .spines end in the u.sual point. 

 The tube feet are placed in three dense series; in the actinal tube feet a well developed sucking di.sk 

 is found. The spicules are small, irregularly branched, rarely with a single hole (PI. XI. Fig. 20); only 

 just below the sucking disk a few larger fenestrated piates are found. They are placed in 2—4 series, 

 but only in the outer part of the foot, nearest to the sucking disk; in the other, larger part of the 

 tube foot only quite few scattered spicules are found, and also in the abactinal tube feet onl\- very 

 few spicules are found. This feature of the spicules also separates this group of species very distinctly 

 from all the other Echinothurid.s. 



The pedicellariæ of these species are especially characteristic (while on the other hånd there is 

 onh- verv little difference in this respect between the species themselves). Only tridentate and tri- 

 phyllous pedicellariæ are found liere, but in return the tridentate ones are found in no less than three 

 well marked forms. In the largest form the blade is narrow, only widened in the point and provided 

 with 2—3 ver}- coarse indentations which work into each other when the pedicellaria is shut; below 

 the blades are then wideh' separated; there are no fine teeth in the edge of the blade (PI. XIV. 

 Figs. 3, 7). Now, to be sure, I ha\'e only seen this form in A. variuin and Gnibci, but I think there 

 is no doubt that it is also found in the two others. There appears, besides, some difference between 

 A. variuin and Gnibci just with regard to this form of pedicellariæ, they being much sienderer in A. 

 varium than in the other; in both they have a length of 2"-2-2'"™ (the head). The neck is quite short. 

 — This difference in the pedicellariæ of the two species indicates that A. Grubci is really a good 

 species, and not synonymous with A. variuin, as Agassiz is inclined to think (Chall. Ech. p. 84). 



The second, smaller form of tridentate pedicellariæ (PI. XIII. Figs. 4, 27) reminds very much of 

 ophicephalous pedicellariæ; but as no indication of arcs is found here, there can be no question of 

 referrino- them to this kind; thev are a highlv modified form of tridentate pedicellariæ. The blade is 

 short and broad, filled by a rich net of meshes, and with 2—3 large indentations in the edge, which is 

 otherwise smooth as in the large form. When the pedicellaria is shut the blades join with the e.xcep- 

 tion of a quite small space at the base. Also this form has a very short neck. The length of the 

 head 1-2 — rs'"™. This form as well as the following one and the triph)-llous pedicellariæ are quite 

 identical in all four species. — On PI. XVI. Fig.s. 10 and 11 in the < Challenger >-Echinids Agassiz 

 gives tolerabl}- recognizable figures of this and the following form of pedicellariæ; — 'darge, short- 

 stemmed) and small-headed, long-stenimed pedicellariæ > they are cailed. PI. XLIV. Fig. 34 Hkewise 

 gives a rather good figure of a valve of the second tridentate form, and Fig. 36 of the third form, 

 which is here cailed <large-headed . But it would be difficult to say what is meant by PI. XEH. 

 Fig. 9, and PI. XLIII. Fig. 2, although the former is given as a dong-headed, long-stemmed >, the latter 

 as a «long-stemmed , small-headed pedicellaria oi A. Grubci. On the other hånd the pedicellaria 



The In^olf-Expedition. IV. i. 7 



