ECHINOIDEA. II. .,- 



thus beiiig number 5; in anotlier case it is the plate V. b. 5 which is expanded, but the 4th plate just 

 touches the episternal plate 5.3.3. — Now ou the Figure 2, PI. XXX. a of the Challenger >-Echinoidea 

 it is seeu to be the 5th or 6th plate which thus expauds; ueither is the fig. 9 on this plate in accord- 

 ance with the rule. This would seem to prove that the specimens represented in these figures cannot 

 be naresiamis (Agassiz also doubts himself, whether the specimen represented in Fig.s. i — 6 is cor- 

 rectly referred to U. iiaycsiamis ( Chall. -Ech. p. 147) and since in U. gigantens it is the 6th anibula- 

 cral plate which expands, the suggestion lies at hånd that they belong perhaps to this species. On a 

 carefnl examination of the specimen represented in Pigs. i — 6, however, I find the plastron of the 

 same structure as in iiarrsiiutus, the 4th ambulacral plate being expanded. The difference in the struc- 

 ture of tlie plastron from the normal condition shown in PI. XXX. a Fig. 2 is due to incorrect drawing. 

 (It is beyond donbt that it is really the specimen, figured in the quoted figures, which I have examined; 

 it quite agrees otherwise with the figures, and also the size agrees — it is ca. 28™'" in diameter, and 

 the figures represent it twice magnified; it is from St. 146.) That this specimen is onlv an abnormal 

 U. naresiamis, as stated by Agassiz (op. cit. 23.148), I think quite certain. — As for the figure 9. 

 PI. XXX. a. it is so indistinct in the delimitation of the piates that it is certainly allowable to suggest 

 that it is also incorrectly drawn. 



The specimens from vSt. 302, which I have likewise examined in the British Museum, differ 

 somewhat from the Atlantic specimens of naresiaiius in regard to the pedicellariæ. The ophicephalous 

 pedicellariæ (PL IX. Fig. 4) have shorter and broader val ves, and likewise the coarse form of tridentate 

 pedicellariæ (PI. IX. Fig. 21) is somewhat different, being more slender than in the Atlantic specimens. 

 On the other hånd, the globiferous pedicellariæ are like those of naresiamis, and likewise the structure 

 of the plastron is the same. Perhaps on a carefnl comparison with the Atlantic specimens this form 

 will prove to be a distinct species; the differences in the pedicellariæ pointed out here are, however, 

 certainly too small for fonnding a new species upon them alone. 



The geographical and batlnmetrical distribution of l^. naresiaiius has thus to be somewhat 

 restricted; it is .stated in the Challenger -Report (p. 218) to occur, from Marion Island to Kerguelen 

 to Australia; Juan Fernandez to Straits of Magellan; Caribbean Islands , at a depth of 1200 — 1800 

 fathoms (on p. 255 it is stated to occur at 422 fathoms at the Caribbean Islands). In reality the species 

 is as yet known with full certainty only from the Atlantic and off South Africa (]Marion Island), from 

 depths of 422 — 1 715 fathoms. 



A few remarks may be given here on Urechimts gigantens Ag., \\ hich I had occasion to exa- 

 niine in the U. S. National Museum, only some fragments, to be sure, but determined by Professor 

 Agassiz himself. ( Albatross S t. 3431.) The structure of the test has been most carefuUy worked out 

 by Agassiz (Panamic Deep-Sea Echini. p. 152), but no mention is made there of the pedicellariæ. 

 They prove to be very characteristic. The globiferous jiedicellariæ (PI. IX. Figs. 2, 6) differ considerably 

 from those of naresiaiius; the blade is an elongate, rather thick tube, which has a large, oval opening 

 on the inside at the point, with 1—3 slender teeth on each side at the outer end; the basal part is 

 comparatively small. The valves are invested with a thick skin, not especialh- thickened over the 

 point, as is the case in iiaresianus. (Probably there will be some kind of glands within the large 

 tube). The stalk as in naresiamis. The ophicephalous pedicellariæ are somewhat more elongate, the 



