ECHINOIDEA. I. 



foot, with the opening directed towards the mouth. The two buccal tube feet are not placed in quite 

 the same line, but one a little outside of the other; this is most distinctly seen in younger specimens, 

 and in quite small young ones of a diameter of up to 2 3 ram only one tube foot of each pair is devel- 

 oped at all. Also in a single specimen of a diameter of 6 mm only one tube foot of each pair of mouth- 

 feet is developed; sometimes it may also be seen that one tube foot is quite wanting in one pair, 

 rudimentary in another, while both the tube feet are well developed in the other pairs. -- A similar 

 feature is found, as stated by Agassiz, in Prioncchinus , or, at all events, in a form by Agassiz 

 wrongly referred to Prioncchinus (see above p. 82 83). Spicules are not found in the buccal membrane, 

 the small gills contain the common irregular calcareous plates (PI. VII. Fig. 12), only, however, in the 

 basal part; spines or pedicellarise are not found on the buccal membrane. 



The apical area is very peculiar, especially in $ a well marked sexual difference being found. 

 In $ the apical area is only slightly raised in the middle (PI. VII. Fig. 9); the ocular plates are small, 

 all widely separated from the periproct, the genital plates are much larger, truncate, rather regularly- 

 septangular, only the boundary line towards the ocular plates somewhat curved. Each genital plate 

 has one rather strong tubercle or a pair of such tubercles at the inner edge, the ocular plates are 

 quite smooth, or more rarely with a few, very small miliary tubercles. The genital pore is very small, 

 situated about in the middle of the plate. The madreporite is very little conspicuous, has only few 

 (2 3) pores. The periproct is covered by one larger plate and some smaller ones; in qiiite small speci- 

 mens the large plate covers the whole periproct. 



In J the mutual relation of the plates is chiefly the same as in <?, but the ocular plates and 

 especially the genital ones have been very much elongated and bent upward, so that the whole apical 

 area is raised like a knob. The lower part of the genital plates and the ocular plates in their whole 

 extent are quite smooth, but the inner (upper) part of the genital plates is very richly set with 

 tubercles forming, as it were, a crown round the upper edge of the knob (PI. VII. Fig. i). The peri- 

 proct as in o", without tubercles. The genital pores are large, and situated nearer to the outer 

 (lower) edge. 



Of pedicellarise only three kinds are found: globiferous, ophicephalous, and triphyllous pedicel- 

 lariae. Tridentate pedicellarias are wanting - - at all events in the specimens in hand. The globiferous 

 pedicellarise (PI. VII. Figs. 19, 20) remind very much of those in <.<Echinus miliaris. The upper ends 

 of the apophysis continue directly in the edges of the blade, which are sharp and run out into 24 

 teeth on either side; there are no cross-beams connecting the edges across the hollow inside of the 

 blade; the end-tooth especially large, of the structure typical in the Echiuids. The glands are quite 

 small reaching only to the basal part; no neck. The ophicephalous pedicellarise (PI. VII. Fig. 18, 

 PI. VIII. Fig. 38) have a quite short neck, but otherwise they do not, any more than the triphyllous 

 pedicellarise (PI. VII. Fig. 16), show conspicuous peculiarities. It is, however, to be noted that in the 

 triphyllous pedicellarise the edge is quite smooth. - The stalks of the pedicellarise consist of longi- 

 tudinal fibres connected by cross-beams to a rather compact reticulation; they are not hollow; they 

 increase evenly in strength downward, but are not widened at the base. - The sphseridise (PI. VII. 

 Fig. 17) show no marked peculiarities; they are slightly spinulous in the point, short-stalked, often 

 somewhat irregular, and more globiform than the figured one. 



