ECHLN'OIDEA. 11. 



/'. hirsiifus and Nordenskjoldi liave the labruiii in contact with tlie sternnni, tliis feature thus evident!)- 

 pointing towards the Urechinids. It thus seems evident that Plexcchinns must be referred to the 

 Urexhinida ; but it must be conceded that the position of the anal system and especially (what Agas- 

 si z seems to have overlooked) the shortened anterior ambulacrum show it to be a somewhat modified 

 type; it is also worth noticing that there is a faint trace of a deepening of the anterior ambulacrum 

 (more distinct even in P. Nordenskjoldi]. These characters point towards the Pourtalesia; and may 

 perhaps indicate that the latter have developed from forms like Plcxechiniis. though the different 

 structure of the paired anterior interambulacra evidently forbid thinking of a direct derivation of the 

 PourtalesicC from the Urrchinida- : the structure of the test of the Pourtalesise is more in accordance 

 with the Echinocorythiinr. and it would, indeed, seem more natural to suggest that the UrrchinidcF 

 and the Pourtalesiidcr are two separate branches from the Echinocorythidce (Ananchytidm). — The 

 resemblances between Plrxechinux and the amphisternous Pahrotropus pointed out bv Agassiz can 

 scarcely be more than superficial analogies. Upon the whole I do not see the reasons why the typical 

 amphisternous PalcBopneustidcv should be reckoned among the Ananchytid Spatangoids , as is done 

 by Agassiz (Panamic Deep-Sea Ech. p. 150). 



Fam. Pourtalesiidae. 



21. Pourtalesia Jeffreysi \V\ v. Thomson. 



IM.V. Fig.s. 13 — 14, 16— 19, 21. 23. in. VII. Figs. 2-4, II— 12, 14, 21. PI, VIII, Fig.s. 4 — 6, 8- 11. PI. XI. Figs. 4, 7— 10, 30. 



Wyv. Thomson: Depths of the Sea. p. 108— 9. Fig. 12. p. 457. (394) Ann. Nat. Hist. 4. Ser. X 

 p. 305. Porcupine -Echinoidea. p. 747. PI. LXX. i — 10. PI. LXXI. — Lovcn: On Pourtalesia. PI. I— V 

 Pi. XII. 149. — Danielssen: Echinida. Nor.ske Nordhavs-Expedition. p. 5. — Pfeffer: (319) p. loi. — 

 Agassiz: Pkhinoidea. (Knight Errant ) (10). — 0stergren: (450) p. 253. — Hoyle: Rev. List British 

 Echinoids. p. 430. — Koehler: (233. b). — Doderlein: Arktische Seeigel. P'auna Arctica. p. 385. Echi- 

 iioiden d. deutschen Tiefsee-Expedition. p. 268. -- Grieg: Echinodermen v. d. norwegischen Fischerei- 

 dampfer Michael Sars in den Jahren 1900 — 1903 gesammelt. I. Ophiuroidea. p. 14. Bergens Mus. Ar- 

 bog. (1903). — Michai lovskij: Zoolog. Ergebnisse d. Russischen Exped. nach Spitzbergen. Echino- 

 dermen. Ann. Mns. St. Petensbourg. VII. 1902. p. 524. Nachtrag. ll)i(l. \'1II. 1903. p. 393. Die Ivchino- 

 dermen der zoologischen Aushcute des Eisbrechers Jcniiak vom vSommcr 1901. Ibid. IX. 1904. p. 163, 

 184. — Kn i ])o wi tsch: Exploratifjus zoologiques sur le bateau casse-glace «Ermak en etc dc 1901. 

 Ibid. \'I. 1901. i>. IX, XV. ~ Knlihoff: Til Spetsbergen och Nordostra Gronlaud Ar igcx). j). 176, 210. 



Xon.: Rathbun: Catalogue of the Echini of the U. S. Nat. Museum. (337) p. 287. ~ Verrill: 

 Results of the Explorations of the Albatross^ 1883 (426). p. 539. — Norman: Notes on the French 

 exploring Vo\age of Le Travailleur in the Ba\- of Bisca\- (302). p. 435. 



The rich and partly well preserved material of this species collected by the Ingolf enables me 



to give a little additional information thereof, though, of course, not much remains to be done after 



the elaborate descriptions given by Wyv. Thomson and especially by Loven 111 his cla.ssical work 



On Pourtalesia . The most needed information, viz. that of the development of the test from ipiile 



