36 PROCEEDINGS OF THE 



PLATE II. 



Fig. 1. Vertical section of a stem, showing a deep concavity on one side 

 tilled with matrix, and a large space excavated in its substance. In the 

 other half of the column this excavation communicates with the central 

 canal. Nat. size. 



Figs. '2-5. Four stems, to which specimens of Productus complectens are 

 attached. They show the various degrees of envelopment by the sub- 

 stance of the Crinoid. Highly magnified. (Copied from the Quart. Jour. 

 Geol. Soc.) 



Fig. G. Section of a small stem, from the Carboniferous limestone of 

 Derbyshire, with a straight direct passage leading towards, but not reaching, 

 the central canal. Nat. size. 



Fig. 7. A stem which has become infested with a colony of Favosites 

 parasitica, over which the Crinoid stem is gradually encroaching from above 

 and below. 



Fig. 8. Microscopic section of au enlarged stem, with some foreign body, 

 probably the cause of the enlargement, lying against the columnar canal. 

 Nat. size. 



Figs. 9-11. Crinoid stems infested with colonies of Cladochonus. In 

 fig. 9 are two enlargements of the stem caused by the different colonies, 

 the terminations of the calices of which are seen protruding from it. Fig. 

 10 is a similar specimen, but with the calices in a better state of preserva- 

 tion, and more free of the Crinoid substance. Fig. 11. Another example, 

 showing the gradual enlargement of the stem, and a siugle line of calice 

 openings. Nat. size. 



Fig. 12. A weathered section of a stem (a) which has been surrounded by 

 a series of corallites of Cladochonus, (b) in their turn now enclosed within 

 the more recently secreted Crinoidal matter. Nat. size. Fig. 12 a . The 

 opposite extremity of the same stem to show the difference in size of the 

 affected and normal condition of the stem. Nat. size. 



Fig. 13. Section of a Crinoid stem, of which the original size is apparent, 

 encircled by calices of Cladochonus, and the whole enveloped in secondary 

 Crinoidal substance. Nat. size. 



Fig. 14. Microscopic section of another stem, from which radiate four 

 corallites of Cladochonus, surrounded by secondary Crinoid substance. 

 Nat. size. 



Fig. 15. A similar specimen, showing a very large calice of a Cladochonus. 

 Nat. size. 



Fig. 16. A fragment of a Crinoid stem, riddled with small circular holes, 

 arranged in cycles. Nat. size. 



Fig. 17. Another, covered with similar holes, but without any definite 

 arrangement. Fig. I7 a . Cross section of the same. 



The subjects of PI. I. figs. 1 to 21, and PI. II. figs. 2 to 5, are from the 

 Scotch Carboniferous limestone series, and are in the Collection of the 

 Geological Survey of Scotland. Those of PI. II. figs. 9 to 11 are in the 

 "Gilbertson Collection;" whilst those of PI. II. figs. 7, 8, 12 to 17, form 

 part of the "Rofe Collection." 



