REPORT ON THE CRINOIDEA. 41 
primary interradials of Thaumatoerinus all end simply in a free rounded edge at the 
margin of the disk (Pl. LVI. figs. 1-3, 5), which is doubtless partly due to the simplicity 
of the arms. For these become free at once, and are not connected laterally by perisome, 
in which higher orders of radials could be supported. The interradial of the anal side, 
however, bears a small tapering appendage of four or five gradually decreasing joints, 
which terminates in a blunt point without any connection whatever with the anal tube 
near it (Pl. LVI. figs. 2, 4, 5). It appears to me to be of the same nature as the so-called 
proboscis of Taxocrinus, Gnormmocrinus, Onychocrinus, &e. The anal plates of these 
genera do not support a huge “ ventral sac,” such as occurs in the Cyathocrinide, but are 
of an altogether different nature. Good figures of them are given by Schultze,’ Angelin,’ 
and by Meek and Worthen.*? They may be advantageously compared with figs. 2 and 
4-on Pl LYVI. 
According to Wachsmuth and Springer‘ the first anal plate of Tuaocrinus “ has a 
truncated upper side, and is succeeded by from two to six similar, narrow, quadrangular 
plates, longitudinally arranged. The plates diminish in size upwards, and form the dorsal 
side of a short and slender lateral proboscis, whose ventral parts, as well as the wall 
supporting them, have never been found preserved, and evidently consisted of more fragile 
material.” A few pages farther on they describe Onychocrinus as follows :—‘ In the anal 
area there is a series of from three to five very narrow, quadrangular plates, which rests 
upon the truncated or slightly excavated upper side of the basal, and forms a small 
lateral proboscis as in Taxocrinus. Interradials three to twenty, perhaps more in some 
species ; the first one large, resting between the first. and second radials, the succeeding 
ones smaller, rapidly decreasing in size and thickness upward, and having an inward 
curvature. They are followed by very minute irregular polygonal -plates, which form 
the interradial portion of the vault.” Meek and Worthen® described this anal series 
as resting upon the larger truncated basal, “ much as the arms of Platycrinus rest upon 
the first radials, and really looking very much like a diminutive arm rising from the anal 
area. This arm-like range of small pieces seems never to consist of more than from four 
to six or seven pieces, which are so small and narrow as to leave a wide open space 
between them and the posterior rays on each side.” Subsequently, however, they met 
with a specimen showing “ the space between the little arm-like range of anal pieces, and 
the radials and vault to be occupied by very numerous minute pieces.”® These last occur 
in each interradius, and are directly continuous with those forming the so-called “ vault ” 
or ventral disk, just in the same way as the perisomic plates between the rays of recent 
Crinoids (Pl. XIII. fig. 1; Pl. XXXIV. figs. 1,2; Pl. L. figs. 1, 2), of Hatracrinus, and 
1 Monographie der Echinodermen des Eifler Kalkes, Denkschr. d. k. Akad. d. Wiss. Wien., Bd. xxvi., 1866, Taf. iv. 
figs, 2, 2b, 3, 4b. 
2 Tconographia Crinoideorum, Stockholm, 1878, Tab. xvii. fig. 8; Tab. xx. figs. 9, 13, 16; Tab. xxiii. fig. 5. 
3 Paleontology of Illinois, vol. v. pl. xiv. fig. 4. 
4 Revision, part ii. p. 46, 5 Paleontology of Illinois, vol. ii. p. 243. 8 [bid., vol. iii. p. 494. 
(ZOOL. CHALL. EXP.—PART XXx1.—1884.) 6 
