57 



slightly in form and size, which are followed by two superior 

 rows of ten pieces each of irregular forms, sometimes there is 

 another at the summit of which completes the field. 



"Interradial fields of the 2d series. Five, composed of pieces 

 similar in form, from six to seven in number, variously ar- 

 ranged, sometimes one surmounted by two similar pieces, these 

 by two others, then a smaller one or one at the base, with one 

 above the other, these again by two ranges of two, then one, 

 all these forms are occasionally found in the same specimen. 



" Interradial fields of 3d series. Usually ten, composed of from 

 three to five pieces not regular in form or arrangement, occa- 

 sionally some of the fields are obscure or absent. 



"Anal pieces six. The first is septigonal and rests upon the 

 large subradial; upon it are two pieces, nearly similar in size; 

 in the angle formed by their junction is one irregular shaped 

 piece supporting two quite small quadrangular ones. 



"The arms are twenty in number, of irregular length, each 

 branch divided into three fingers, making sixty in all. They 

 are free from the third or fourth piece of the third division. 



"The arrangement of the several series of interradial fields 

 between the branches of the arms produces a very large cup 

 in proportion to which the rays are quite short. The general 

 form of our species is somewhat like that of lehthyocrinus 

 loevis (Courad) Hall's figure, New York Geol. Rep. pi. 48 fig. 2. 

 In the arrangement of the rays and the interradial fields in 

 three series it approaches Forbesocrinus wortheni Hall (Iowa pi. 

 17, fig. 5) from which it differs widely in the number of anal 

 pieces. 



"Our specimens are nearly perfect, none of them exhibit the 

 patelloid pieces of F. Woriheni Hall. In several species of 

 this genus which have come under our observation there are 

 no patelloid pieces, in a few of our specimens (the prolonga- 

 tion of the superior pieces near the center of their breadth 

 overlapping the inferior) some of the prolongations are frac- 

 tured; specimens of this character have probably led to the 

 remark of Mr. Hall before cited. It is highly probable that 

 this prolongation in the living animal was less calcareous than 

 the remainder of the piece and owing to this circumstance was 

 differently mineralized from the mass of the piece. This very 

 difference, in the composition of the pieces, supposing that the 

 prolongation was cartilaginous and the rest of the piece 

 bony, would give flexibility to the body of the calyx and 



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