1886.] NATURAL SCIENCES OF PHILADELPHIA. 163 



pieces, with a pore at each angle. Column pentagonal, with 

 rounded angles. 



Decadocrinus agrees closely with Graphiocrinus, but the latter 

 has no azygous plate, only an anal piece. 



Additional species : 



a. With simple brachials. 



*1882. Decadocrinus columbiensis (Worthen), Poteriocrinus columbiensis, Bull. 



i, 111. 8t. Mus. Nat. Hist., p. 22; also Geol. Rep. Illinois, vii, p. 293, PI. 19, 



fig. 6. Kaskaskia limest. Monroe Co., 111. 

 *1882. D. fountainensis (Worthen), Poteriocrinus fountainensis, Bull, i, 111. St. 



Mus. Nat. Hist., p. 17; also Geol. Rep. Illinois, vii, p. 286, PI. 30, Fig. 



11. St. Louis limest. Monroe Co., 111. 

 *18S1. D. Milleri (Wetherby), Poteriocrinus Milleri (not Worthen), Journ. Cincin. 



Soc. Nat. Hist. (January), PI. 9, figs. 12, 13. Kaskaskia gr. Pulaski 



Co., Ky. 

 *18S2. D. penicilliformis (Worthen), Poteriocrinus penicilliformis, Bull, i, 111. St. 



Mus. Nat. Hist., p. 8; also Geol. Rep. Illinois, vii, p. 276, PI. 28, fig. 9. 



Keokuk limest. Hamilton, 111. 

 1882. D. zethus Williams. Proc. Acad. Nat. Sci. Phila., p. 27, PI. I, fig. 9. Port- 

 age gr. Ithaca, N. Y. 



b. With compound hracMals. 



1882. D. gregarius Williams. Proc. Acad. Nat. Sci. Phila., p. 22, PI. 1, figs. 6, 7, 8. 

 Chemung gr. Ithaca, N. Y. 



WOODOCRINUS De Koninck. Rev. i, p. 124. 



(Emended W. and Sp.) 



Syn. Parisocrinus W. and Sp. Rev. i, p. 115. 



Syn. Zeacrinus Hall (not Troost) in part. Geol. Rep. la., vol. i, p. 544. 

 Syn. Zeacrinus Sladen, 1877. On the genus Poteriocrinus, etc., p. 7. 

 Syn. (.?) Philocrinus De Koninck, 1862. Quart. Joum. Geol. Soc, London. 



The ventral side of Woodocrinus has not been observed, but 

 we may suppose from the spreading of the arms that its sac was 

 rather bulk3^ This is further suggested by the great width of 

 the azygous side, which, however, is composed of the same 

 elements as in most Poteriocrinites, and is not structurally dis- 

 tinct as has been generally supposed. It has, like Poteriocrinus, 

 within the calyx three azygous plates the succeeding pieces 

 forming the abactinal parts of the ventral sac which for some 

 distance, are exposed between the arms. It differs from Scaphio- 

 crinus in the shortness of its arm joints and arms generally. 

 This it shares, however, with Pachylocrinus as defined by us, and 

 with Zeacrinus Troost. 



