ORDER III CRINOIDEA—FISTULATA 161 
Gurley. Although agreeing with this family in a general way, they are readily dis- 
tinguished from the typical forms by certain characters which they possess in common 
with the Encrinidae. The dorsal cup is saucer-shaped, and composed of heavy plates ; 
the articular faces of the radials are provided with well-marked muscular fossae ; the 
arms vary from uniserial to biserial within the limits of the same genus ; and the ventral 
sac is reduced to a small cone, extending but little above the level of the ventral disk. 
These genera, according to Wachsmuth and Springer, constitute, together with the 
genus Encrinus, a group which is sufficiently distinct to be recognised as an inde- 
pendent family. 
European writers, on the other hand, have almost without exception agreed in 
associating Encrinus in the same category with recent Crinoids ; the reasons for this 
being partly because it is a Mesozoic form, partly because it has axial canals along the 
inner floor of the dorsal cup, and, finally, because anal plates are wanting. But the 
imaginary line which was formerly conceived as separating the Palaeozoic from the 
Neozoic Crinoids, has now been generally abandoned ; and as axial canals have been 
found to exist among Palaeozoic forms as well as among the later ones, the only vital 
distinction remaining is the presence or absence of anal plates. 
In point of fact anals are present in most of the above-named genera. Cromy- 
ocrinus and Eupachycrinus have both an RA and IRA; Phialocrinus has only the 
IRA, and Ulocrinus only the RA, but Stemmatocrinus and Hrisocrinus agree with 
Encrinus in having neither JRA nor RA, Hence, if the division between the Poterio- 
crinidae and Encrinidae be established simply upon the presence or absence of anal 
plates in the cup, Stemmatocrinus and Erisocrinus are necessarily included under the 
latter family, and the remainder excluded. But if other characters be chosen as 
criteria, such as the mode of articulation, and the reduction of the ventral sac, then 
all of the above genera must be included in the same family with Encrinus. The latter 
course appears preferable ; especially since the gradual disappearance of anals may be 
regarded as a natural consequence of the decrease in size of the ventral sac. Adopting 
this course, the family Encrinidae may be defined as follows :— 
© Calyx more or less saucer-shaped, with dicyclic base. Infrabasals five, small, generally 
concealed beneath the top stem-joint. Articular faces of the radials forming a horizontal line, 
and completely occupied by the first costals; faces provided with large muscular fossae, and a 
perforated transverse ridge. Costals one or two. Ventral sac rudimentary ; anal plates gener- 
ally absent. Tegmen (in Encrinus) elevated, composed of rather heavy plates. Arms usually 
ten, rarely five or fourteen ; pinnule-bearing. Carboniferous and Trias. } 
Cromyocrinus, Trautsch. (Fig. 267). Dorsal cup low, cup- or saucer-shaped. 
IB moderately large, always projecting beyond the column. Jha large ; 
RA barely touching the ventral sac; no plates of the latter 
entering the dorsal cup. Costals one to each ray. Arms 
ten, rarely five; uniserial or slightly interlocking from 
opposite sides. Column round. Carboniferous Limestone ; 
Moscow, Russia. Kaskaskia Group; Mississippi Valley. 
Eupachycrinus, M. and W. Dorsal cup as in the preced- 
ing genus, but the ZB much smaller, and concealed by the 
column. B large. JRA and FLA both represented; the 
latter very large, and supporting a small plate of the ventral pitts 
tube, the lower part of which descends into the cup. ATMS — Gpo;yoerinus globulus, 
generally ten, rarely five or fourteen ; either uniserial, inter- M. and W.. Sub-Car- 
° 5 : = : EP tbe eke boniferous ; Chester, 111. 
locking, or biserial. Kaskaskia Group; Mississippi Valley. Natural size after Meek 
: . : . . and Worthen). 
Ceriocrinus, White (Delocrinus, Miller and Gurley). “ : 
Dorsal cup as in the preceding, but the posterior & more elongate than the 
others, and supporting a small /?4 , upper end of the latter extending above 
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