56 



RCHINOIDEA. I. 



cellarise is found, the large and small ones being upon the whole constructed in the same way. They 

 are finely serrate in the edge. The neck long, the stalk of the common structure. The length of the 

 head up to i - 5 mm . The triphyllous pedicellariae of a very fine form, with well-developed cover-plate, 

 without holes (always?), and the edge beautifully serrate (PI. XII. Fig. 14). — The spicules are in the 

 lower part of the tube foot almost rod-shaped, with a few holes in the middle (PI. XL Fig. 19); they 

 are placed in two series, across the longitudinal axis of the foot. In the upper part of the tube foot 

 the}- are larger fenestrated plates; the sucking disk well developed. The tube feet in three series, 

 beautifully trigeminate as in an Ecliinus. The primary spines on the actinal side curved, with a rather 

 long hoof almost not thicker than the spine. Besides the characters mentioned here, there seem to be 

 found good characters in the structure of the test and in the apical area; with regard to these char- 

 acters the reader is referred to the description by Agassiz. It is evident that this species cannot 

 be referred to any of the other genera; especially characteristic are the globiferous pedicellariae, to 

 which nothing corresponding is known in other Echinothurids. It must form a separate genus, for 

 which I propose the name of Hapalosoma 1 ). 



Of the species that have been referred to Asthenosoma, the two species A. longispinum and 

 Iijamat from Japan described by Yoshiwara (448), are still left to be mentioned. Of these nothing 

 can for the present be said with certainty; A. longispinum, however, seems to be a Calveria or an 

 Arceosoma. 



Phormosoma fame A. Ag. (A specimen from Challenger st. 237 examined). The tube feet are 

 placed very close together, forming only one almost regular series. The spicules highly developed, 

 irregular fenestrated plates. There is no distinct sucking disk, only some irregular, slightly branched 

 or unbranched continuations passing from the outermost fenestrated plates of the foot into its point. 

 The primary spines on the actinal side ending in a little hoof. Only tridentate and triphyllous pedi- 

 cellariae are found. Of tridentate pedicellariae a larger and a smaller form are found. The larger form 

 (of which a rather good figure is found in Chall. Ech. PI. XLII. Fig. 7, and PL XLJV. Fig. 19) has a 

 rather rich, coarse net of meshes in the lower part of the blade, and the upper end of the apophysis 

 continues somewhat into the blade as a serrate crest (PI. XII. Fig. 35). This crest is not distinctly seen 

 in the figure in Chall. Ech. (PI. XLJV. Fig. 19), possibly it may not be a constant feature. The length 

 of the head up to 2'8 mm . The smaller form (the head up to i mm ) reminds much of those in Ph. placenta, 

 but the contour is somewhat different, and the widenings from the upper end of the apophysis reach 

 to the edge of the blade (PI. XII. Fig. 40). The neck is long, also in the larger form, the stalk of the 

 common structure. The triphyllous pedicellariae have a well developed cover-plate; the edge finely 

 serrate. -- I have not found the peculiar two-valved, bottle-shaped pedicellaria figured by Agassiz 

 (Chall. Ech. PI. XLJV. Fig. 21). As it is two-valved, it may be taken to be an abnormity. It is, no 

 doubt, a modification of the triphyllous pedicellariae. This I also take to be the opinion of Agassiz 

 when he says (op. cit. p. 82), that perhaps it is only a modification of « the remarkable long-pronged 

 pedicellariae figured by Thomson as characteristic of the group > 2 ). — In the description of this species 



') dxaXtig — soft. 



\ few lines lower down in the same paragraph Agassi/, seems to derive this form from the tridentate pedicel- 

 lariae (see above p. 46). 



