266 SMITHSONIAN INSTITUTION 



Wenlock area, as the locality of its occurrence is not stated, although its owner called it the 

 " superior part of the Derbyshire encrinite." 



In 1839 Phillips 1 described and figured as Cyathocrinites pyriformis a well-marked 

 specimen somewhat similar to that of Ellis (Parkinson's pi. 19, fig. 2). He recognized, 

 however, its strongly distinctive structure, and stated that it " ought probably to constitute 

 a new genus," pointing out as its characters " the great width, general equality and lateral 

 union of the plates, till the arm divisions amount to twenty." 



Hall 2 in 1843 referred Phillips's species to Conrad's genus, and expressed the opin- 

 ion that the species described by the two authors from England and America respectively 

 were identical. 



D'Orbigny 3 in 1849 accredited the genus Ichthyocrinns to Conrad, defining it as 

 follows : " Calice composee de quatre series de pieces. Cinq pieces basales." His idea of 

 its character was rather indistinct, for while following Hall in referring to it C. pyriformis 

 along with /. laevis, he included also several species now ranged under Gissocrinus, in which 

 the characters pointed out by both Phillips and Hall as peculiar to the new form are wholly 

 wanting. 



Hall 4 took up the discussion of the genus again in 1852 in connection with a more 

 elaborate description of /. laevis, with ample illustrations showing new and important 

 details. After quoting Conrad's generic definition, which he thought not sufficiently precise, 

 he stated that the cup consists of five small, triangular pelvic plates, succeeded by three 

 scapular plates followed by two or three subdivisions ; and he added : " The base of the cup, 

 when the column is separated, presents a tripetalous impression, which is probably of generic 

 importance. This genus .... possesses peculiarities of high interest, showing its 

 relations to crinoids with three pelvic plates." This is the first allusion in the literature of 

 this group to a dicyclic base. Pie confirmed this statement in 1858 5 in his generic formula, 

 where he said there were " sometimes three other rudimentary plates within the five basal 

 plates." 



M'Coy 6 in 1854 gave a description of Ichthyocrimts in considerable detail, crediting it 

 to Conrad in conjunction with D'Orbigny, without whose suggestion he thought " the figure 

 and description of Mr. Conrad would not have been definite enough to establish this 

 genus " ; — though wherein D'Orbigny's definition contributed to its elucidation is difficult 

 to see. M'Coy defined the generic characters to be : column round, the calyx composed of 

 5 pelvic plates (Basals) ; 5 first, second, and third primary radials, the last supporting two 

 rows of secondary radials of 4 joints each, etc. He added however the important observa- 

 tion that " the absence of interradial plates separates this genus from Taxocrimis" ; this was 

 confirmed by Salter in his Catalogue of 1873, as the sole difference between the two genera. 



Bronn 7 in i860 defined the genus as irregular, having 5 basals, no subradials, 4, 1 x 3 

 radials, and no anals nor interradials. Neither M'Coy nor Bronn made any allusion to the 

 existence of five undeveloped pelvic plates (infrabasals), nor had Roemer done so in Bronn's 

 Lethaea Geognostica in 1856. 



Angelin s in 1878 recognized three basals and five parabasals, the former sometimes 

 obsolete ; but he introduced a new complication by giving also one anal plate between the 

 lower radials — a statement not warranted by any of his specimens. 



1 In Murchison, Silurian System, vol. 2, p. 672, pi. 17, fig. 6. 



2 Geology of the Fourth District, New York, p. 112. 



* Prodrome de Paleontologie, vol. 1, p. 46. 



1 Nat. Hist. New York, Paleontology, vol. 2, p. 195. 



5 Geology of Iowa, vol. 1, pt. 2, p. 557. 



6 British Palaeozoic Fossils, p. 54. 



7 Klassen und Ordnungen des Thier-Reichs, Bd. 2, p. 231. 



* Icon. Crin. Suec, p. 13. 



