520 FRANK SPRINGER 



EXPLANATION OF PLATE IV 

 Onychocrinus ulrichi M. and G. 



Fig. I. — The ventral disk or tegmen complete, except as to one ray, which is 

 broken off; view from above, anterior side at the top. It shows the pyramid of four 

 small orals at the center, two of them very plain, the third less so, and the fourth, at 

 the left, pushed in under the others and invisible from this view; the large posterior 

 oral with the ambulacra running along the sides, and the anal appendage bent over 

 to the right under its posterior margin. The rows of ambulacral plates are seen 

 extending from the oral pyramid to and along the rays, with the plated integument 

 between them. The whole disk is now concave, having sunk down into the bottom 

 of the calyx, and the view of the large posterior oral is somewhat foreshortened. The 

 infolding ramules of the arms are well shown in two of the rays. 



Fig. 2. — The disk of another specimen, seen from the under side — the calyx 

 plates having been removed; posterior side up. This shows the same structures as 

 Fig. I, only viewed from the opposite side. The opening between the orals, and the 

 undulating under surface of the posterior oral, are well shown; also the keeled inner 

 surfaces of the ambulacrals. 



Fig. 3. — Disk of another specimen, same view as in Fig.i; showing the same 

 structures, but with the curved anal appendage in plain view, and a portion of the 

 plated integument, or perisome, attached to it at the right. The orals are much dis- 

 placed, and the view of the posterior one greatly foreshortened; a row of strong plates 

 proceeding from the shoulders of the posterior oral is well preserved in this specimen, 

 perhaps serving as a brace for the tegmen. 



Fig. 4. — Detail of central part of disk from another specimen; to show the per- 

 forate structure of the posterior oral. In order to get a better light on this plate, 

 the specimen is drawn with posterior side up. This specimen shows but little 

 aside from the posterior oral; the anterior orals are in position, in a more advanced 

 stage of resorption than those in the other specimens; the round object at the right 

 is probably a foreign body. The granules in the tegmen seem to be somewhat larger 

 than usual. X2. 



Fig. 5. — Dorsal view of calyx and two complete rays, showing this aspect of the 

 anal appendage. 



Thaumatocrinus renovatus p. H. Carpenter 

 Fig. 6. — View of the disk from above; showing the oral pyramid, the marginal 

 zone of small plates between the orals and the interradials, and the anal tube with 

 its appendage of strong plates. The protuberances seen between the arm-bases are 

 the interradials, which separate the radials all around. (After P. H. Carpenter, Philo- 

 sophical Transactions, Plate 71, Fig. 5. X15.) 



(All figures except 4 natural size). 



EXPLANATION OF PLATE V 

 Antedon rosaceus 



Fig. I. — Early Pentacrinoid larva, spirit specimen, \vith its tentacular apparatus 

 retracted; showing basals, radials, and rudimentary primibrachs, and the orals opened 

 out. (From W. B. Carpenter, Plate XXXIX, Fig. lA. X15.) 



Fig. 2. — The same, at a somewhat later stage, spirit specimen; showing incipient 



