REFORT ON THE CRINOIDEA. 41 



primary interradials of Thaumatocrimis 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 tul)c 

 near it (PI. LVI. figs. 2, 4, 5). It appears to me to be of the same nature as the so-called 

 proboscis of Taxocrinus, Gnorimocrinus, Onyclwciimis, &c. The anal plates of these 

 genera do not support a huge " ventral sac," such as occurs in the Cyathocrinida), but are 

 of an altogether different nature. Good figures of them are given by Schultze,' Augelin,'' 

 and by Meek and Worthen.^ They may be advantageously compared with figs. 2 and 

 4 on PI. LVI. 



According to Wachsmuth and Springer* the first anal plate of Taxocrinus " 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 (PI. XIII. fig. 1 ; PI. XXXIV. figs. 1,2; PI. L. figs. 1, 2), of Extracrinus, and 



1 Monographie der Echmodernien des Eifler Kalkes, Denkschr. d. k. Akad. d. IFiss. IFiai., Bd. xxvi., 1866, Taf. iv. 

 tigs. 2, 26, 3, 46. 



2 Iconographia Crinoideorum, Stockholm, 1878, Tab. xvii. fig. 8 ; Tab. xx. figs. 9, 13, 16 ; Tab. xxiii. fig. 5. 



3 Paleontology of Illinois, vol. v. pi. xiv. fig. 4. 



4 Revision, part ii. p. 46. « PaL-eontology of Illinois, vol. ii. p. 243. « Ibid., vol. iii. ]). 494. 



(^OOL. CIIALL. EXP. — P.^RT XSXII. — 1884.) Ii (J 



