EXPLANATION OF PLATE 53. 87 



and entirely composed of a mass of petrified Ossicula 

 of the same species of Pentacrinite. The surface of 

 these fossils is covered with a delicate film of Iron 

 Pyrites, which gives them the appearance of beauti- 

 ful Bronze. (Original.) 



l a . Continuation of the stem of Fig. 1. 



2°. Portion of the stem of Fig. 2. 



The length of these stems when entire, was three 

 or four times that of the fragments here remaining. 



Upon the stem 2 a , nearly all the side arms retain 

 their places in the grooves on each side of the salient 

 angles of the pentagonal column ; they diminish in 

 size as they approach its upper extremity. This is 

 also distinctly seen at the upper end of the column 

 of Fig. 1. 



— First costal plate. — Second costal plate. 



Fig. 3. Portion of a third column retaining nearly all its 

 auxiliary side arms in their natural place. 



Fig. 3?. Continuation of the same column deprived of the 

 side arms. 



Fig. 4. Portion of another column, with traces of a few 

 side arms rising from the lateral grooves. 



Fig. 4 a . Continuation of Fig. 4. 



Fig. 5. Fragment of another column, the joints of which 

 are so much bent without dislocation, as almost to 

 give the column the appearance of a spiral disposi- 

 tion. 



Fig. 6. Body of a Briarean Pentacrinite and summit of 

 its column, showing the interior of the ossicula that 

 surround the abdominal cavity. 



E. Pelvis. -^- First costal Plate. From a specimen in the 

 Oxford Museum. (Original.) 



Fig. 7. Fragment of a column in the collection of Mr. 

 J. Sowerby, showing the oblique articulation of the 



