MORPHOLOGY 



35 



Figs. 1-5 

 funnel lodging the chambered organ j stem-lumen ; and course of dorsal nerve cords. 



ia. Ichthyocrinus; IBB too minute to support funnel, which here rests upon basal ring; 

 chambers coincide with IBB sutures and are therefore interradial in position; but in their 

 downward passage the cords are revolved until they become radial in the stem. X 10. lb, 

 dorsal view of same, showing radial orientation of stem-lumen. X 10. ic, diagram showing 

 course of nerve cords. 



2a. Forbesiocrinus saffordi; chambers coincide with IBB sutures, are interradial and 

 pass into the stem in that position; small IB exceptionally at anterior. X 5- 2b, diagram 

 showing probable course of paired nerve cords — those of large IBB compressed into about the 

 space of a single cord. 



3. Course of nerve cords in dicyclic calyx, drawn from Pycnosacctis. 



4. Course of nerve cords in monocyclic calyx with unequal basals as shown by external 

 ridges, drawn from Stephanocrinus angulatus. 



5. The same in monocyclic calyx with equal basals, drawn from Steganocrinus 

 pentagonus. 



