64 SMITHSONIAN INSTITUTION 



PLATE IV 

 Calyx plates, Pinnules, and Sculpturing 

 (All figures natural size unless otherwise stated) page 



Scyphocrinus elegans Zenker 30 



Fig. 1. A composite figure, constructed from the original of fig. 1, PI. V, and speci- 

 mens A, B, C, D, E, F, G, of the slab shown on PI. I. 



To show development of the fixed pinnules, and the way in which 

 they lose their identity by the progressive change in surface sculpturing 

 produced by modification of fine grooves and costas in lower part into 

 stronger depressions and ridges upward, until the appearance becomes 

 that of transverse bands suspended between the rami, instead of longi- 

 tudinal series. In one ray and part of an interradius the surface orna- 

 ment is omitted, and to facilitate identification the pinnulars are left 

 unshaded while the interpinnulars and intersecundibrachs are indicated 

 by diagonal hachure. Thus the succession of pinnules upon IIBr 

 2-4-5-6-7 is shown, until at about the eighth IIBr the interpinnulars 

 disappear, and from there on the pinnules are packed in close lateral 

 contact. The distal ends of the pinnules from the IIBr and lower IIIBr 

 bend over and become merged in the tegmen, as shown in PI. Ill, 

 fig. $b. The extreme relative shortness of the IIIBr is well shown, 

 and also the manner in which the first few pairs of them are joined by 

 their inner margins. The limit of the calyx distally is seen to be 

 approximately just above the level of the IIIBr axil. 



2. Part of a ray from IBrj to bifurcation at IIBr 20 ; showing the various 



styles of sculpturing at different levels caused by progressive changes 

 in the size and form of pits and ridges passing from plate to plate. 

 Made from specimens A and E. 



3. Portion of the right side of interradius above illBr ; showing the change 



in superficial appearance of the interbrachial pavement due to modifica- 

 tion of the depressed areas at the angles of the plates by lateral coales- 

 cence into continuous furrows, producing the transverse girdles or 

 chains. Constructed from specimens A and B, and fig. 1 of PI. V. 



4. Side view of section of a ramus at the lower IIIBr, with the pinnules 



closely abutting proximally by angular faces, x 2. 



5. Cross-section of brachial and pinnule at same level, x 2. 



6. Oblique dorsal view of IIIBr, showing modified articular face of brachial 



and connecting pinnules, also the angular faces of pinnulars abutting 

 upon those of adjoining pinnules, x 6. 



7. 8. Cross-section of pinnule on lower IVBr and VBr. x 2. 

 9. Cross-section of pinnule at lower VIBr. x 2. 



10. Side view of portion of arm at VIBr between those of figs. 9 and 11, show- 



ing pinnules rounded and beginning to be free from their fellows, x 2. 



11. Cross-section at higher VIBr. x 2. 



