NATURAL HISTORY SOCIETY OF GLASGOW. 35 



DESCRIPTION OF PLATES I. AND II. 



PLATE I. 



Fig. 1. A swollen stem of Poteriocrinus crassus?, from Roscobie Quarry, 

 Fife. Nat. size. The aperture is seen near the centre of the stem iu an 

 elongated depression, and filled with a plug of matrix. 



Figs. 2 and 3. Sections of fig. 1, taken at various heights, to show the 

 aperture and passage leading to the central canal and the mass of black 

 matrix which extends throughout the canal for some distance. Nat. size. 



Fig. 4. Another swollen stem from Bathgate, taken from the non- 

 perforated side. Xat. size. 



Fig. 5. The section of Fig. 4 cut directly across the passage. Xat. size. 



Fig. 6. A stem — from the Edinburgh neighbourhood — in which there is 

 a large oval depression resembling Miller's original figure in the Natural 

 History of the Crinoidea, Nat. size. 



Fig. 7. Section of the same stem, in which the passage leads direct to the 

 central canal from the external depression. Nat. size. 



Fig. 8. Vertical section, in which the connection between the external 

 depression in the stem, the passage leading from it, and the canal is quite 

 apparent. Nat. size. 



Fig. 9. A horizontal section, showing a direct, somewhat triangular 

 passage. The section has been cut a little above the communication between 

 the latter and the canal. Nat. size. 



Figs. 10 to 12. Horizontal sections of small stems, showing the shallow 

 pocketdike passage not communicating with the canal. Fig. 10, Nat. size. 

 Figs. 11 and 12. x 2. 



Fig. 13. Cross section of another small stem, in which the aperture shows 

 a tendency to split into two passages. x 2. 



Fig. 14. A small stem, showing two small apertures, such as lead into 

 pockets represented in Figs. 10-13. x 2. 



Fig. 15. A similar specimen, with one circular hole. Nat. size. 



Fig. 16. A Crinoid stem, on which there has been an adherent Polyzoon 

 now in course of enclosure. Nat. size. 



Fig. 17. The Polyzoon, with enclosing Crinoidal matter enlarged. It 

 appears to be a species of Archaeopora. x 2. 



Fig. 18. Swollen stem, with two apertures almost along the line of 

 fracture, x 3. 



Fig. 19. The fractured surface of Fig. 18, showing the passage into which 

 the two apertures led, and occupied by what appears to be an Annelide 

 tube, x 3. 



Fig. 20. Vertical section of an uninjured stem, to show the mode of 

 articulation of the auxiliary side-arms. Nat. size. 



Fig. 21. Horizontal section of an uninjured stem, to show the same thing. 

 Nat. size. 



