CRINOIDEA FLEXIBILIA 55 



Figs. 1-27. Forbesiocrinus nobilis De K. and Le H. (continued) 249 



Fig. 13. Secundibrach i, proximal articulating face. The left side is truncated to meet its fellow 

 above the axillary. 



14. Right lateral face of another specimen of same rank. 



15. Secundibrach 2, distal articulating face. 



16. Left lateral face of another plate of same rank. 



I7a,b,c,d. Secundibrachs 3 and 4; dorsal, ventral, left lateral, and distal faces. The ventral 

 surface is no longer concave, and has become marked by more or less distinct longi- 

 tudinal ridges and grooves for the attachment of perisome, with which the transverse 

 lateral grooves seem at times irregularly to connect (shown also in figs. 20-22). 

 The rugose margin has become proportionally narrower, and the thickness of the 

 plates has increased to two-thirds their width. 



t8, 19. Tertibrachs i and 2, proximal articulating faces. 



20,21,22. Ventral surface of tertibrachs i, 2 and 3; showing the varying appearance of the 

 longitudinal grooves, and the rugosity upon the lateral face ; this has become narrower 

 and is gradually disappearing. 



23. Quartibrach, distal face. The plates have now become as thick as wide, and the lateral 

 rugosity has disappeared. 



24a, b. Brachials of fifth order ; lateral and distal views. 



25a, b, c. Brachials of sixth order ; lateral, dorsal, and ventral views. 



26a, 6, c. Brachials of seventh order ; lateral, dorsal, and distal views. 



The last three series of plates are dissected from the incurved arms of the specimen 

 figured on Plate XXIII, figs, la, and le, and their position is authentic. The brachials 

 have here become relatively very thick and narrow, with a well defined median longi- 

 tudinal groove on the ventral side flanked by another one on either side. From what 

 is observed in the corresponding parts of Synerocrinus incurvus (PI. XLII, fig. 56), it 

 is clear that these grooves and the partition between them formed the lodgement for 

 small plates of a perisomic integument, which may have taken the form of ambulacra 

 over the median groove at this stage. They are enclosed by strong projections at the 

 margins of the plates, producing a concave ventral surface, in contrast to the flatness, 

 or even convexity, in the intermediate radial divisions. 



27. Lateral face of brachials in a fragment of an abnormal ray from specimen figured 10, 

 PI. XXIII, showing a radial articulation, with rugose lateral face above and below it. 

 Natural size. 



All the specimens are from the Tournai Stage, Lower Carboniferous ; Tournai, 

 Belgium ; and are in the author's collection. 



Figs. 28, 29. Forbesiocrinus sp 248 



Figs. 280, b, c. A radial. Dorsal, distal, and lateral views of an isolated plate found in strata 

 equivalent to the Kinderhook-Lower Burlington, at Lake Valley, New Mexico. It has 

 the same deep lateral fossae seen in the Belgian specimens. Author's collection. 

 29a, b. Secundibrach I, from same locality. Distal and inner lateral faces, the latter being the 

 sutural union with its companion plate above the axillary. Author's collection. 



