Bd. VI: 4) THE ECHINOIDEA. 5 I 



place the author himself expresses some doubt regarding the correctness of the 

 identification, and in the latter paper the species diadema, horridus and antarcticus 

 are given as synonymous, it is evident that these statements of the occurrence of 

 the species in the Antarctic sea cannot be taken into account. 



The fact that the species St. Agassizii, diadema and antarcticus appear to have 

 only a very restricted distribution (diadema known only from the Kerguelen-region, 

 antarcticus only from the coasts of the Antarctic Continent) would seem to indicate 

 that these species have not pelagic larvae, because in that case they would probably 

 have a much wider distribution, as is the case with St. Neumayeri, which is known 

 (through the researches of the German South Polar Expedition) to have pelagic 

 larvae. The size of the eggs in these species seems to point to the same conclusion, 

 those of St. Neumayeri being distinctly smaller than those of the other three spe- 

 cies. (Cf. Echinoiden d. Deutschen Sudpolar-Exp. p. 96. Note.) 



The genus Sterechinus, established by KOEHLER (Echinides et Ophiures du 

 »Belgica», 1901, p. 8) for the species antarcticus, was extended by me in the »Ingolf» 

 Echinoidea I (p. 106) to include also the species »margaritaceusi> (including diadema), 

 horridus, Neumayeri and magellanicus. DODERLEIN (Echinoiden d. deutschen 

 Tiefsee-Exped. 1906, p. 217) again excluded magellanicus, making it the type of a 

 separate genus, Notechinus, and thus gave the genus Sterechinus a much more uni- 

 form character. In »Stellerides, Ophiures et Echinides* de l'Expedition Antarctique 

 Francaise, 1906, p. 36 — 39, KOEHLER again maintains the genus in its original sense, 

 including only the species antarcticus, but recently, in »Asteries, Ophiures et Echi- 

 nides de l'Expedition antarctique nationale Ecossaise», 1908, p. 618 he explains that 

 he now fully adopts my view on this matter, as corrected by DODERLEIN. There 

 is thus now full agreement on this point between all those authors, who have treated 

 these species recently. 



The fact that the distinguishing characters of the species within this genus are, 

 upon the whole, of comparatively slight value, seems to indicate that the species 

 have been comparatively recently differentiated, probably in connection with the 

 geological transformations in these regions (subsidence of the former land or 

 shallow-water connection between South America and the Kerguelen-group on one 

 side and between South America and the Antarctic Continent on the other side). 

 It may be suggested that before this subsidence they were represented by a single 

 species distributed along the coasts of this whole extensive land. Through the sub- 

 sidence the specimens inhabiting the intermediate regions were exterminated, leaving 

 the rest inhabiting three isolated areas; in the course of the time elapsed since the 

 epoch of the subsidence the three groups of specimens have been transformed into 



