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 
Platycrinus.” These two genera, however, are both Palzeocrinoids ; but Belemnocrinus 
and Rhizocrinus, a Paleocrinoid and a Neocrinoid respectively, are related im precisely 
the same way. The former, like Edriocrinus, has an anal plate in line with the radials ; 
while there is no such structure in Rhizocrinus nor in Cotylecrinus. The arms of 
Edriocrinus are more numerous than those of Holopus, as there are secondary axillaries 
beyond those in the radial series; but they were rolled in on one another very much after 
the manner of the Holopus-arms; and this was also the case in the Devonian 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 :2—*‘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 
ealeareous 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, which eventually 
removed all traces of the scar denoting the previous attached condition of the individual. 
The Mesozoic and recent Holopide do not seem ever to have passed into the “free” 
condition characteristic of Agassizocrinus and Hdriocrinus, 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 Paleozoic 
Edriocrinus.’ For I find it difficult 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 Hyocrinip, P. H. Carpenter, 1884. 
Genus Hyocrinus,’ Wyville Thomson, 1876. 
Definition.—Calyx high, and composed of basals and radials which are nearly equal in 
length. The former narrow gradually downwards, 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 Paleontology of Illinois, vol. iii. p. 371. 2 Natural History of New York, Paleeontology, vol. iii. p."120. 
3 [hed., p. 143. 4 Revision, part i. p. 21. 5 Ann. and Mag. Nat. Hist., ser. 5, vol. xi., 1883, pp. 327-834 
6 Named after Hog Island, one of the Crozets. 
(uooL. CHALL, EXP.—PART Xxx1L—1884.) Ji 28 
