212 CATALOGUE OF THE BLASTOIDEA. 



it is proposed to describe these, and restore the name proposed by that pioneer of 

 Western geology, Dr. Troost." Conrad's name appears to have been entirely unknown 

 to Lyon, whose analysis of the calyx was far more elaborate than that given by 

 Roemer, and, except in one point, has not met with general acceptance. 



Two years laler Messrs. Lyon and Casseday in their " List of Palaeozoic Echino- 

 dermata of North America " x pointed out the identity of Nucleocrinus, Conrad, 

 OHvanites, Troost, and Elceacrinus, Roemer 2 ; and they abandoned Troost's name 

 in favour of that previously proposed by Conrad, OHvanites and Elceacrinus being 

 thus reduced to the rank of synonyms. 



Three years later the same course was taken by Hall 3 , who made no reference, 

 however, to Messrs. Lyon and Casseday. He carefully excluded from Elceacrinus, 

 or, as he termed it, Nucleocrinus, such species as Pentremites Norwood!, O. & S., and 

 P. melo, O. & S., which have a calyx very similar in form to that of Elceacrinus, 

 though, so far as we are aware, neither Roemer nor any one else had ever proposed 

 to place them in this genus. He altogether ignored Lyon's analysis of the calyx, 

 but gave one of his own which, except for one important point (the intercalated 

 anal plate), is almost identical with that previously published by Roemer. 



The next year (1863), Dr. F. B. Shumard, in a paper entitled " Descriptions of 

 new Palaeozoic Fossils," 4 also suggested the probable identity of Nucleocrinus and 

 Elceacrinus, but he included therein most of those Blastoids which form Roemer's 

 group Elliptici (i. e. Granatocrinus and Cryptoblastus, as we now understand them). 

 Shumard's previously conceived views were, however, changed in 1865 5 , when he 

 restricted Elceacrintis within much the same limits as were originally proposed by 

 Roemer. In the same year those accomplished Palaeontologists, Messrs. Meek and 

 AVorthen, clearly laid down the characters which separate this genus from Granato- 

 crinus 6 as typified by G. Norwoodi and G. melo ". 



We now come to the views of Elwacrinus which Avere expressed by the late Mr. 

 Billings in his note, " On the Structure of the Genus Nucleocrinus.'''' 8 He adopted 

 and supported the theory of Mr. S. S. Lyon, regarding the presence of a second 

 series of concealed basal plates ; while he also described the interradial plates as 

 quite small and as bounded by marginal pieces which belong to the ambulacra. 



The genus Nucleocrinus and Hall's diagnosis of it were accepted by Montgomery !> 



1 Proc. American Acad. 1859, vol. iv. p. 283. [This volume bears date 1860, and is for the period 

 extending from May 18.57 to May 1800. Shumard, however, in his " Catalogue of the Palaeozoic Fossils 

 of North America. — Part 1. Echinodcrmata " (Trans. St. Louis Acad. Sci. 1SG5, p. 33-1 ), gives the date 1859 

 to Lyon and C'asseday's paper (/. c. p. 309), which we here adopt.] - Ibid, p. 295. 



: Fifteenth Ann. Rep. New York State Cab. Nat. Hist. 1S62, p. 146. 



4 Trans. St. Louis Acad. Sci. 1863, vol. ii. no. 1, p. 1 12. ■"■ Ibid. 1865, vol. ii. no. 2, p. 363. 



8 Keport Geol. Survey Illinois, 1806, vol. ii. p. 27">. 



' This species is erroneously described as having single spiracles perforating the deltoids. 



8 American Journ. Sci. 1870, vol. 1. p. 229. 



■• Canadian Nat. & Geol. 1881, vol. x. no. 2, p. 80. 



