III. Lebetodiscus Dickson /'. 



1908 543 



III. Lebetodiscus, n.g. for Agelacrinites Dicksoni, Billings. 1 

 [Geol. Mag., n.s., Dec. V, Vol. V, pp. 543-550, PI. XXV ; Dec, 1908.] 



Previous History. 



rPHE specimen herein to be considered is one of great historical 

 J interest, for it was the first specimen of an Edrioasteroid made 

 known to science. It was discovered by Dr. J. J. Bigsby in limestone 

 now recognised as of Lower Trenton age, forming Table Bock at the 

 Chaudiere Falls on the Ottawa River at Ottawa (then called Bytown), 

 Canada, in 1822. Brought by Bigsby to England, it was figured and 

 described, though not named, by G. B. Sowerby in 1825. 2 E. Eorbes, 

 who had the specimen for study, referred to it in his memoir " On the 

 Cystideae of the Silurian Bocks of the British Islands," 3 since the 

 " aspect" of his Agelacrinites Buchianus " immediately called [it] to 

 mind"; he even went so far as to say that there could 41 be no 

 question ... of its being genetically allied" to that species. 

 Considering the not unnatural inadequacy of Sowerby's description 

 and figure, the reputation that Forbes had as an authority on 

 echinoderms, and the comparative imperfection of the first found 

 specimens of Edrioaster, it was not surprising that E. Billings in 

 1856 4 should have supposed a new Trenton fossil, undoubtedly 

 congeneric with Agelacrinites Buchianus, to be of the same species as 

 that found by Bigsby, and should therefore have applied to it the 

 trivial name ' Bigsby while giving to a fossil of obviously different 

 structure the name 'Agelacrinites Dicksoni. 1 b In February, 1858, 

 Billings travelled to London with the fossils in question, and found 

 that Bigsby 's specimen was not, after all, the same as his Cy clatter 

 Bigsbgi, but it was specifically identical with his A. Dicksoni. He 

 redescribed the species, and had his type-specimen, as well as Bigsby's 

 fossil, figured by C. ft. Bone. 6 



The latter specimen was said by Billings to be then " in the Museum 

 of Practical Geology, Jermyn Street, London." I therefore supposed 

 that it had been transferred to the British Museum when all the 

 foreign fossils were so transferred some years ago. But when no trace 

 of it could be found either in the collections or the registers of that 

 establishment, I applied to Mr. E. T. Newton, palaeontologist to the 



1 Publication of the present Study, written in 1899, was delayed OAving to an 

 unwillingness to load Zoology with a new generic name without further continuation 

 from all available evidence. Since that date so much Edrioasteroid material has 

 passed through my hands that the publication of these Studies is resumed with more 

 confidence. 



2 " Notice of a Fossil belouging to the Class Radiaria, found by Dr. Bigsby in 

 Canada" : Zool. Journ., vol. ii, pp. 318-20, pi. xi, fig. 5 ; London," October, 1825. 



3 Mem. Geol. Surv. Gt. Brit., vol. ii, pt. ii, 1848 ; see pp. 519 and 520. 



4 Rep. Progress Geol. Surv. Canada, 1853-6, p. 292 ; Toronto, Autumn of 1857. 



5 Op. cit., p. 294. 



6 Canadian Organic Remains, dec. iii, p. 84, pi. viii, figs. 3 and Za (the holo- 

 type), 4 and 4a (Bigsby's specimen). 



