GENEEA AND GEOUPS OF THE ECHIITOIDEA. 271 



dredging in Davis's Straits an unknown Echinoderra was got. 

 This form, with a great number of Invertebrata, was confided to 

 the Rev. A. Norman for description. In June 1876 Mr. Norman's 

 report was read before the Royal Society, as forming part 

 of that of the director of the Expedition (Proc. Roy. Sec. xxv. 

 pp. 202-215, June 1876). The notice is excellent, and it is stated 

 before the description, " a remarkable new genus of Echinoidea 

 occurred here." On p. 212 it is written, " This new and most 

 interesting form will be named Aerope rostrata by Sir "W. Thom- 

 son ;" and there is a footnote, " When this description was read 

 I had suggested a name for the present species ; but having since 

 learnt from Sir W. Thomson that it has also been procured in 

 the ' Challenger'' Expedition, I gladly adopt the above name 

 under which I found that he was about to describe it." The 

 ' Challenger ' returned in May 1876. 



Sir Wyville Thomson handed over the Echini of the ' Chal- 

 lenger ' to their able describer A. Agassiz in 1876, who pub- 

 lished a differential and critical definition of the genus Aerope 

 in the official report, 1881. 



He left Mr. Norman out of the matter, and his references 

 to the Royal Society's Proceedings by mistake relate to Sir 

 W. Thomson instead of Mr. Norman. A. Agassiz wrote, ' Chal- 

 lenger ' Report, p. 190, that the genus was first described 

 by Sir "W. Thomson in the Voyage of the ' Challenger,' vol. ii. 

 p. 28 (correct reference vol. i. p. 380). There is no doubt 

 that A. Agassiz had not had the opportunity of knowing that 

 Mr. Norman's description was the best and earliest. 



Grenus Aerope (described without a name, 1876, A. Norman, 



Proc. Boyal Soc. 1876, p. 211), Wyv. TJwjnson, 1877, Voyage 



of the ' Challenger,^ Atlantic, vol. i, p. 380, fig. 90. A. Agassiz, 



1881, Report on the ' Challenger ' Echini, p. 190, pis. sxxiii., 



xxxiii a. 



Test small to rather large, rather stout, very elongate, generally 



cylindrical, higher than broad, oval and acuminate posteriorly, 



slightly rounded in front in marginal outline, and sloping anteriorly, 



highest centrally, and convex actinally behind the peristome. 



Apical system excentric in front, within the anterior slope, 

 with four basal plates, perforated, the ducts ending in as many 

 tubes ; madreporite in the right anterior plate extending to the 

 centre ; antero-lateral radial plates small, and separating the 



