^8 ECHUMOIDEA. II. 



/'. Iiirsutus and Nordenskjoldi have the labruiii in coiitact with tlie sternum, this feature thns evidenth- 

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

 Urechinida; but it must be conceded that the position of the aual system and especiallv (what Agas- 

 siz seems to have overlooked) the shortened anterior amlDulacrum show it to be a somewhat modified 

 t\'pe; it is also worth noticiug that there is a faint trace of a deepening of the anterior ambulacrum 

 (more distinct even in P. N^ordciiskjuldi). These characters point towards the Pourtalesiæ and mav 

 perhaps indicate that the latter have developed from forms hke Phxrcliiiius, though the different 

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

 Pourtalesiæ from the Urechinida- ; the structure of the test of the Pourtalesiæ is more in accordance 

 with the Echinocorythinæ . and it would, indeed, seem more natural to suggest that the Urcchinidcr 

 and the Poiirtalesiidæ are two separate branches from the Echinocorythidce (Ananchytidæ). — The 

 resemblances between Plcxcchinus and the amphisternous Palæotropus pointed out bv Agassiz eau 

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

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

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



Fam. Pourtalesiidæ. 



21. Pourtalesia Jeffreysi W\ v. Thomson. 



Pl.V. Fij<s. 13 — 14, 16-19, 21, 23. PI. VII. Figs.2-4, 11-12, 14, 21. PI, VIII. Figs.4-6, S II. 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. — Loven: On Pourtalesia. PI. I— V 

 PI. XII. 149. — Danielssen: Echinida. Nonske Nordhavs-Expedition. p. 5. — Pfeffer: (319) p. loi. — 

 Agassiz: Echinoidea. ( Knight Errant ) (10). — Ostergren: (450) p. 253. — Hoyle: Rev. List British 

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

 noiden 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. År- 

 bog. (1903). — Michailovskij: Zoolog. Ergebnisse d. Russischen Exped. uach Spitzbergen. Echino- 

 dermen. Ann. Mus. St. Petersbourg. VII. 1902. p. 524. Naclitrag. Ibid. VIII. 1903. p. 393. Die Echino- 

 dermen der zoologischen Ausbeute des Eisbrechers Jermak vom Sommer 1901. Ibid. IX. 1904. p. 163, 

 184. — Knipowitsch: Explorations zoologiques sur le bateau ca.sse-glace Ermak en été de 1901. 

 Ibid. VI. 1901. p. IX, XV. — Kolthoff: Til Spetsbergen och Nordostra Gronland Ar 1900. p. 176, 210. 



Non.: 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 Voyage of Le Travailleur in the Ba>- of Bisca>- 1302). p. 435. 



The rich and partly well jsreserved 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 in his classical work 



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



