REPORT ON THE CRINOIDEA. 217 



from the Upper Silurian of North America, appears to be very closely allied, to the recent 

 Holopus and to Cotylecrinus. According to Meek and Worthen/ it seems to differ from 

 this last type " only in having an anal piece on the same range with the first radials, the 

 relations between the two groups being exactly the same as between Hexacrinus and 

 Platijcnnus." These two genera, however, are both Palaeocrinoids ; but Belemnocrinus 

 and RMzocrimis, a Palseocrinoid and a Neocrinoid respectively, are related in precisely 

 the same way. The former, like Edriocri7Xus, has an anal plate in line with the radials ; 

 while there is no such structure in Rliizocrinus nor iu Cotylecrimis. The arms of 

 Edriocrmus are more numerous than those of Holopus, as there are &«econdary axillaries 

 beyond those in the radial series ; but they were rolled in on one another very much after 

 the manner of the Holopus-Sixms; and. this was also the case in the Dewomsji. Lecanocrinus 

 roemeri, Schultze. The latter type has a stem ; but this organ appears to have been 

 altogether absent in Edriocrinus, which is thus described by Hall:- — "These Crinoids are 

 sessile in the young state, adhering singly or in groups to other substances until fully 

 developed, when they are separated from the foreign bodies, and gradually secreting 

 calcareous matter to cover the cicatrix or point of adhesion, become finally smooth 

 rounded bases." Elsewhere ^ again he described the radial plates as proceeding from this 

 " short pedicle " as from the summit of a column. According to Wachsmuth and 

 Springer* this pedicle really consists of five closely anchylosed, basal plates, with the 

 sutures between them obliterated by a secondary calcareous deposit, W'hich eventually 

 removed all traces of the scar denoting the previous attached condition of the individual. 

 The Mesozoic and recent Holopidse do not seem ever to have passed into the "free" 

 condition characteristic of Ag(issizocrinus and Edriocrinus, so that there is no scar of 

 attachment to be obliterated. But I strongly suspect that the subradial portion of the 

 body, centro-dorsal, support, cupule, or whatever it be called, consists either wholly or 

 (more probably) in great part of anchylosed basals, just as it does in the Palaeozoic 

 Edriocrinus.^ For I find it diflicult to believe in the existence of a family of Crinoids 

 which are normally devoid of any basal plates, as these are of fundamental importance 

 both in the morphology of the Crinoids, and in that of Echinoderms generally. 



Family Hyocrinid^, P. H. Carpenter, 1884. 



Genus Hyocrinus,^ Wyville Thomson, 1876. 



Definition.— Caljx high, and composed of basals and radials which are nearly equal in 

 length. The former narrow gradually downw^ards, while the latter are broad and spade-like, 

 each bearing a small undivided arm in the middle of its upper edge. Arm -joints united 



1 Palaeontology of Illinois, vol. iii. p. 371. - Natural History of New York, Pateontology, vol. iii. p."120. 



3 Ibid., p. 143. * Eevision, part i. p. 21. ^ Ann. and Mag. Nat. Hist., ser. 5, vol. xi., 1883, pp. 327-334 



^ Named after Hog Island, one of the Crozets. 

 (ZOOU CHALL. EXP. — PART SXXII. — 1884.) li 28 



