ECHINOIDEA. II. 



97 



emphasized by Agassiz. It is mainly the large frontal tiibe-feet which are takeii as a proof of this 

 affinity — < the striking resemblaiice of the youiig Brissopsix with its gigantic stickers in the odd 

 anterior ambnlacruni (Rev. of Ech. PI. XIX. i — 2) to tlie fnll-grown Aerope, plainh- shows the Hrissoid 

 affinities of the genus» (<:Chall. -Ech. p. 190); but also the sha2:)e of the test is, if I nnderstand it rightly, 

 taken as a proof of this affinity (tChall. -Ech. p. 196). Quite apart from the faet that it seenis rather 

 exaggerated to term the frontal tube-feet of the young Brissopsis gigantic , this isolated feature, the 

 large frontal tube-feet, does not appear to me a sufficient proof of near relation between thcse othcr- 

 wise very different types; the subanal fasciole so characteristic of Brissopsis seems especially a proof 

 against the suggested affinity with Aeropsis and Accstr. Also the structure of the globiferous pedi- 

 cellariæ is a proof against more close affinity of these forms, far more important tlian a i)ossil)le 

 resemblance in the shape of the test of Accsfc when secn in end view. 



If the view expressed above (p. 84—85) of the primary classificatory importance of the structure 

 of the sternum be correct — of which I for my part am fully convinced — it naturally follows that the 

 affinities of Aeropsis and Accstc to Pourtalesia and other Ananchytid genera, likewise repeatedly emph- 

 asized by Professor Agassiz, are not real; the}' are merely superficial analogies. Aeropsis and Ae es te 

 are rather primitive amphisternous forms, which cannot Ijc more closely related to the higher meri- 

 dosternous genera, and neither can they be taken as showing the passage of the Poiirfalesia-<gxo\v^ 

 to the Bri.ssina among the Spatangoids^ («Chall. -Ech. p. 190). 



26. Hemiaster expergitus Eovén. 



I'l. II. Figs. I, 4, iS, 20. PI. IV. Fig.s. 6— 8, 10 — 12. PI. XV. Figs. 9, 16—18, 24, 26, 30—31, 35, 38, 44—45, 47—48, 50. 



Synonyms: Hemiaster zonatus A. Ag. 



— gibhosjis A. Ag. (? — see below, p. 102 — 5). 



— Mentzi A. Ag. 



Literature: Loven: Etudes sur les Échinoidée.s. p. 13. PI. V. 46— 47. XI. 93— 94. XIII. 114— 20. 

 XXVI. — On Pourtalesia. p. 53. PI. X. 92. XVIII. 222. — Bernard (78). — Th. Mortensen: Some new 

 species of Echinoidea. p. 243. 



The specimens of Tlciuiastcr dredged by the Ingolf , Michael Sars and Thor must un- 

 donbtedly be referred to the species described by Loven, 1 [. expergitus. Profes.sor Théel most kindly 

 sent me the type specimens of Loven so that I have been able to make a direct comparLson, and 

 the identity is thus estabHshed beyond doubt. The species was hitherto recorded, .since Loven, only 

 from the «Talisman by Bernard, and it is thus a faet of no .srnall interest that it uow ])roves to 

 occur also in the northern Atlantic, and evidenth- not ver>- rareh-. The specimens before me are of 

 different sizes, from 5""" to 37""" in length; I have further taken a quite young specimen of only 3""" 

 length off Frederikssted, St. Cruz, ca. 500 fathom.s, which evidently belongs to the same .species. (Loven 

 had only a pair of young specimens of 10—14™'" length). We are thus al)le to follow the changes 

 which appear with age. 



The shape of the test is seen from the figures representing the naked test and the test with 

 the spines (PI. II. Figs. i, 4, 18, 20. PI. IV. P'ig.s. 6— 8, 10— 12). The outline is oval, a little broader m the 

 anterior half. The abactinal side is almost flat, sloping rather .strongly from behind towards the front, 



The Ingolf-Expedition. IV. j. I ^ 



