ECH|I;NIDAE 219 



distinct variety. The reason why I do not follow H. L. Clark (Hawaiian Echini, 

 Pedinidae. . . Echinometridae, p. 262; Cat. Recent Sea-Urchins Brit. Mus., p. 113) in 

 regarding afitarcticus as a simple synonym of S. diadema (Studer) — with which latter 

 also S. Agassizii and Netimayeri are united as simple synonyms — is because the typical 

 afitarcticus is a very characteristic form and apparently mainly confined to the Antarctic, 

 whereas both diadema and Agassizii are mainly sub-Antarctic. That antarcticus and 

 Agassizii meet off South America, the former extending as far north as South Shetlands, 

 perhaps South Georgia, the latter as far south as South Georgia, the two forms thus 

 meeting there, is a natural consequence of the geography of this region. Very probably 

 the two forms also interbreed here, this adding to the difficulty of distinguishing them 

 clearly in all cases. If they did occur together over their whole area, I should not hesi- 

 tate to regard them as only one very variable species ; but so far as at present known each 

 of them has its own area of distribution. Therefore I do not think it correct simply to 

 regard them all as one single species, as does Clark. That diadema, Agassizii (formerly 

 " margaritaceus") and antarcticus are very closely related and evidently only local 

 specializations of one single, original species I quite agree. As for S. neumayeri I do not 

 think it so closely connected with the other three forms, but quite a distinct species, 

 though it also evidently interbreeds with antarcticus (or Agassizii), which makes some 

 specimens, very probably hybrids, difficult to refer with certainty to one or other form. 



Sterechinus Neumayeri (Meissner) 



(Plate II, figs. 1-4) 



Sterechinus Neumayeri, Mortensen, 1909. Deutsche Siidpolar-Exped. Echinoiden, p. 64, 

 Taf. vii.fig. 7;viii, fig. 6;ix, figs. 2, 6-7, 9, 11-13, 15; xvii, figs. 2-6, 8, 12-14, 17-18, 22-23, 



27. 29- 

 5. Neumayeri, Mortensen, 1910. Swedish South Polar Exped. Echinoidea, p. 42, pis. vi, 



figs. 7-8; vii, figs. 1-2, 4. 

 S. Neumayeri, Koehler, 1912. IP Exped. Antarct. Fran9aise. Echinodermes, p. 160, pi. xiii, 



fig. 1. 

 For other literary references see the work of 1909, loc. cit. 



St. 141. 29. xii. 26. East Cumberland Bay, South Georgia, 17-27 m. i specimen. 



St. 163. 17. ii. 27. Paul Harbour, Signy Island, South Orkneys, 18-27 "i- ^^ specimens. 



St. 164. 18. ii. 27. Normanna Strait, Coronation Island, South Orkneys, 24-36 m. Several 

 specimens. 



St. 173. 28. ii. 27. Port Foster, Deception Island, South Shetlands, 5-60 m. Several specimens. 



St. 371. 14. iii. 30. I mile E of Montagu Island, South Sandwich Islands, 99-61 m. i specimen. 



St. 1489. 17. i. 35. Port Lockroy, Wiencke Island, Palmer Archipelago. On the beach, at low 

 tide. I specimen. 



St. MS 71. 5. iii. 26. East Cumberland Bay, South Georgia, 110-60 m. 2 specimens. 



St. MS 73. (No information.) South Georgia. 3 specimens. 



St. MS 74. 17. iii. 26. East Cumberland Bay, South Georgia, 22-40 m. 2 specimens. 



The specimens from St. MS 71 are unusually lightly coloured and have a rather 

 close resemblance to S. Agassizii; quite probably they are hybrids between these two 

 species. 



