56 



ECHINOIDBA. II. 



sliowing some tendenc)- to dissohitioii in this gronp. To determine with certainty which of the otlier 

 piates in the apical area of this species onght to be regarded as basal or as »intercalated piates is 

 scarcely possible, and I cannot feel convinced either that the interpretation of these piates in P. ciiictns 

 given by Agassiz is quite correct. — The genital openings are present in a specimeu of 13'""', but 

 have not yet appeared in a specimen of 11"'". 



The primar\- tubercles are scattered quite without order over the whole test, except the ambu- 

 lacral piates joining the sternuni and episternuni. A great nuniber of small tubercles are found aniong 

 the primary ones. On the primar\- interambulacral piates, which are all in contact with the peristome, 

 the tubercles ma\' be rather numerous, forming like a rudimentary bourrelet. The larger ones of the 

 piates of the peristome mav carry a single tubercle (spine). — The primary spines (PI. X. Figs. 21,31) are 

 ca. 3™™ long, slender, gracefully curved, more or less spinous, a little widened towards the point. The 

 spines of the sternum are rather widened in the point and hollowed (PI. X. Fig. 38). The spines round 

 the actinostome are not distincth' clubshaped. The railiary spines (PI. X. Fig. 32) are short, ca. O'S""; 

 the point is widened and serrate, more or less flattened. The clavulæ of the fasciole do not differ from 

 the other miliary spines. 



The tubefeet of the two or three inner ambulacral piates are penicillate, forming a rather con- 

 spicuous phyllode. The rods supporting the filaments of these tubefeet are irregularly fenestrate, rather 

 coarse (PI. X. Fig. 37); the spicules (PI. X. Fig. 27) are arranged in two series; tliey are of the same general 

 shape as in Urec/iiiiiis. The tubefeet of the anterior ambulacrum are rather large, but simple; a more 

 or less distinct calcareous ring, formed by some few irregular, fenestrate piates is found, at the point 

 of the simple tubefeet. — The sphæridiæ are found onl\- on the inner one or two pairs of ambulacral 

 piates, generally only one on each plate. They are rather elongate, smooth (PI. X. Fig. 25). 



The pedicellariæ are represented by the four usual forms. The globiferous pedicellariæ (PL X 

 Figs. 23, 34) are very peculiar; the blade forms a short but ratlier wide tube, which ends with a large 

 round opening, sometimes prolonged a little downwards on the inside; the edge of the opening is 

 rather finely serrate, e.xcept on the lower side. No neck; the stalk is rather thick. — It ma\', indeed, 

 be regarded as a little doubtful whether this form realh- represents the globiferous pedicellariæ, since 

 there is no thick skin covering the valves, as is the case in the related genera Urecliiiiits etc. But 

 on the other hånd it is rather similar in structure to the undoubted globiferous pedicellariæ of Urc- 

 chiiiHS gigantens, IVyvillii etc, and it would be more unnatural to refer it to any of the other kinds 

 of pedicellariæ. (The glandular tissne may perhaps be found within the tubeshaped blade). The triden- 

 tate pedicellariæ (PI. X. Figs. 2, 16, 36) are small, the largest ones only ca. 0-3'"™. The blade is .simply 

 leafshaped, sometimes shorter and almost round; the edge is serrate, generally with some longer 

 teeth at the point. The figure 15. PL X represents a somewhat different form, with the blade more 

 narrow and the apophj-sis ending down in the blade. I have not seen transitional forms between the 

 two kinds of tridentate pedicellariæ. The ophicephalous pedicellariæ (PL X. Fig. 19) are ver\- simple, of 

 the usual structure; the upper end of the .stalk cupshaped. The triphyllous pedicellariæ (PL X. F'ig. 17) 

 differ only little in shape from those of Urccliiiuis. — The pedicellariæ of this species are upon the 

 whole few in number and little conspicuons. 



The species was taken at the following stations by the Ingolf : 



