1004 ME. p. A. BATHER OJf UINTACBINUS. [Dec. 17. 



6. EXPLANATION OP THE PLATES. 

 Plate LIV. 



Structure of Uintacrinus socialis. 



Fig. 1. The apical system of specimen e, iu E 6327. X 3. 



Eig. 2. Articular or joint surface of a normal brachial, showing oblique fulcral 



ridge. X 10. 

 Fig. 3. Ditto. X 24. 



Fig. 4. Joint-surface of a syzygial brachial. X 9. 

 Fig. 6. Ditto. X 10. 

 Fig. 6. Joint-surface of a normal brachial from the proximal region of the 



arm. x 6. 

 Fig. 7. Joint-surface of a normal brachial. X 4. 



Fig. 8. Joint-surface of a normal brachial from the proximal region of the 

 arm ; the two halves of the fulcral ridge appear to be at an angle 

 to one another, x 13. 

 Fig. 9. Joint-surface of a normal brachial, showing at top right-hand comer 



the facet for the pinnule. X 4. 

 Fig. 10. Joint-surface of a normal brachial ; the fulcral ridge runs in a direction 



at right-angles to that in figs. 2 & 3. X 4. 

 Fig. 11. Portion of an arm, showing origin of pinnules, the fourth joint from 



the right is a syzygy. x 4. 

 Fig. 12. Joint-surface of a pinnular, showing axial canal with ligament-depres- 

 sion on either side. X 30. 

 Fig. 13. A single brachial, bearing on its right side a pinnule, of which ten 



ossicles are preserved. X 6. 

 Fig. 14. Portion of a pinnule from the ventral side ; the pinnulars are slightly 

 shifted, so that portions of their proximal joint-surfaces are seen. 

 X 12. 



Figs. 1, 11, 12, 13, 14 are by F. O. Pickard Cambridge, the rest by the 

 author, and are all taken from E 6327. 



Plate LV. 



An attempt at an exact i-estoration of Uintacrinus socialis, represented as 

 swimming, five alternate arras raised, and five in the act of depression. The 

 various twists and coils of the arms are but slightly modified from actual speci- 

 mens. The length of the arms is based on calculations from the specimens 

 (see pages 987-8). The drawing was made of the natural size, by Mr. F. O. 

 Pickard Cambridge, under the direction of the author, and has been reduced 

 photographically to about one-sixth natural size. 



Plate LVI. 



Uintacrinus socialis. 



This is a reproduction of Clark's (7) plate i. from Bull. U.S. Geol. Surv. 

 no. 97. The electrotype of the original block was very kindly sent by Mr. C. D. 

 Walcott, Director of the U.S. Geological Survey, and my best thanks are due 

 to him for permission to use it. 



Fig. la. "Lateral view of the test, with interradial area central, natural size." 

 This clearly is taken from one of the specimens figured by Meek (3). 

 Compare text-figure 2, page 976. 



Fig. 16. "Test with arms." This also is doubtless natural size. 



Fig. 1 c. "A radial \i. e. interdistiehal] area, magnified two diameters." 



