58 SMTTI-ISONIAN INSTITUTION 



PLATE XXVI 

 (All figures natural size except where otherwise stated) 



PACK 



Figs. 1-2. Forbesiocrinus agassizi Hall (continued) 250 



(Also on Plates' XXI, XXV) 



Fig. la. Lateral view of large, flattened specimen, showing nearly full length of arms. 



I&. Dorsal view of IBr, showing form of patelloid process and socket of proximal and distal 

 ends respectively. X 1- 



ic. Axillary IBr, dorsal view; showing same structures. X 2. 



20. Proximal end of stem with IBB fused to top 'joint the full width of column exteriorly, but 

 sloping to a small pentagon at the interior. 



2&. Ventral view of IBB in same specimen, showing impression of BB and relative size of 

 IBB pentagon at the interior. 



2c. Interior of IBB enlarged, showing form and position of channels passing down into 

 column. By oversight the suture between the two large IBB is drawn bisecting the 

 septum, whereas it coincides with the angle of the large channel just above. This 

 funnel is irregular in the apparent position of the small IB, which is probably a 

 greatly reduced compound plate, while the simple infrabasal should be the one at the 

 top of the figure, here enlarged to include the whole of the uncompressed lobe to the 

 right instead of only half of it. X 4- 



.2d. Cross-section of base, showing flat position of IBB; composed from this and other 

 specimens. 



Upper Burlington limestone. Burlington, Iowa. 



All the specimens are in author's collection. 



Figs. 3-5. Forbesiocrinus burlingtonensis n. sp 253 



Fig. 3a. Mature specimen vertically compressed, showing three IBr; posterior view. Author's col- 

 lection. 

 3&. Basal view of same, drawn with anal side down. Author's collection. 

 3c. Distal view of same, showing infolded arms. , 



4. Anterior view of specimen but little flattened, showing extremely sinuous sutures and 



gibbous plates. Mus. Comp. Zool. 



5. Posterior view of similar specimen, showing tendency of anal plates to form a vertical 



series at the right (the apparent bifurcation shown in the drawing is misleading). 

 The patelloid projections here occupy over half the width of the plates and strongly 

 modify the form of the median elevation. Author's collection. 

 Upper Burlington limestone. Burlington, Iowa. 



