ECHINOIDEA. I. ^j 



One more locality niay be added for this species, viz. ,Albatross> 1885, st. 2415, near Plorida 

 (30" 44' N. Lat., 79^ 26' W. L., 440 fathoms) as, according to what has been mentioned above, a specimen 

 received from U. S. National Museum under tlie name of Porocidaris Sliarrcri has proved to be iden- 

 tical with the species described here. I suppose that it has oftener been confounded with other 

 Cidarids. At present, however, it is only known with certainty from the stations enumerated here: on 

 the ridge south of Iceland, between Icehind and Greenland towards the ridge here separating the 

 Atlantic from the Polar basin, and at Florida. The depth is 170 — 633 fathoms; accordingly it seems 

 to be no genuine deep-sea form eitlier. 



Recent species of the genus Stcreocidaris have first been described from Japan by D 6 d e r 1 e i n 

 (Die japanischen Seeigel. 116); a species of the same genus, St.indica Doderl. (118) has later been taken 

 by Valdivia» in the Indian Ocean in many piaces and in many varieties, of which a couple, to judge 

 from the preliminary description, seem to be so very like .57. iiigol/iafia, that it will be difficult to 

 distinguish between them; but Prof. Doderlein, to whom I have sent a specimen oiSt.ingolfiana for 

 exaniination , has informed me that he thinks the two species to be good ones. With the species 

 described here the occurrence of the genus also in the Atlantic is jiroved; this genus thus appears to 

 be cosmopolitan. 



4. Porocidaris purpurata Wyv. Thomson. 



PI. VI. Kig. 12. PI. VIII. Kig. 22. PI. X. Figs. I — 2, 5. PI. XI. Figs. 3, 21. 



Synonym: Porocidaris gracilis Sladen. 



Wyv. Thomson: Echinoidea of Porcupine; (395) p. 728. PI. LIX. & LXI. 14 — 15. — Bell: 

 Catalogue (73) p. 141. - Hoyle: 202. p. 405. — Sladen: 367. 



With regard to this easily distinguished species I have only little to add to the excellent 

 description by Wyv. Thomson. 



The ambulacral areas: Inside the outer, primary series of tubercles a somewhat smaller 

 tiibercle is found in the lower corner of each jjlate, and moreover a quite small tubercle below the 

 primar\- one, which accordingly does not fill up the whole breadth of the plate. There is, however, 

 some irregularity; one or the other of the small tubercles are not rarely wanting, sometimes both of 

 them. Also the pores are different from those of the other Cidarids mentioned here, as will be seen 

 by a comparison of the figures (PI. VI. Fig.s. 8— 9, 11 — 12). 



The spicules are arranged in the tube feet as in D. papillata\ the two series, however, do not 

 always join closely, naked spaces are often seen between them, in which only a few spicules are 

 joining. They are somewhat complicated, the thorns on the outer side coalescing and forming a more 

 or less distinct net of meshes (PI. XI. Fig. 21). 



Of the very charactcristic two-valved pedicellariæ Wyv. Thomson (op. cit. p. 729) says: ■>Their 

 structure is in every way the same as that of the ordinary three-valved pedicellariæ, except in the 

 number of the valves. All the usual chambers and ridges are developed, and the different muscles 

 are very evident through the transparent walls>. In this statement I do not agree with Wyv. 

 Thomson. These pedicellariæ are highly different in structure from common tridentate pedicellariæ, 

 with which they must most nearly be compared (PI. X. Fig. i, 2, 5). They have no apophysis; the whole 



The Ingolf-Expedition. IV, I. 6 



