158 PEOCEEDINGS OP THE ACADEMY OP [1886. 



a. Poteriocrinites. 



POTERIOCRINUS J. S. Miller. 



Rev. I, p. 111. 



Dorsal cup obconical ; plates delicate and frequently covered 

 with wrinldes or radiating plications. Radials with a semicir- 

 cular scar, facing outward, and provided with a transverse artic- 

 ular ridge. Brachials one ; laterally constricted ; sutures gaping. 

 Arms long and branching ; composed of wedge-formed plates. 

 Ventral sac long, constructed of six longitudinal rows of short 

 transverse plates forming a tube ; one of these rows resting upon 

 the anal piece, another upon the third azygous plate. The plates 

 of the tube, which are heavier along their median line, are pro- 

 vided laterally with transverse ridges or plications, which all have 

 long open slits along their margins. Column circular. 



We add the following species to our list : 



1882. Poteriocrinus Clarkii Williams, Proc. Acad. Nat. Sci. Pliila., p. 21, PI. 1, fig. 



4. Chemung gr. Steuben Co., N. Y. 



Var. alpha, ibid., p. 22, PI. 1, fig. 5. Chemung gr. Ithaca, N. Y. 

 1882. P. cornellianus Williams, Proc. Acad. Nat. Sci. Phila., p. 18, PI. 1, figs, 1, 2, 



3. Chemung gr. Ithaca, N. Y. 

 1836. P. impressus Phill. (not McCoy, 1854 = Hydreionocrinus McCoyanus, nor 



Richter and linger, 1860). Geol. Yorkshire, p. 205, PI. 4, fig. 1. Austin, 



1843, Rec. and Foss. Crin., p. 10, fig. 6. W. and Sp., Rev. i, p. 120. Sladen, 



1877, On the Genus Poteriocrinus, p. 8. Bristol, England. 

 1882. P. otterensis Worthen, Bull, i. 111. St. Mas. Nat. Hist., p. 14 : also Geol. Rep. 



Illinois vii, p. 283, PI. 28, fig. 4. Otter Creek, Jersey Co., III. 



Species having the characters of the Poteriocrinites, but not sufficiently known 

 to be referred to the proper genus : 



P. aemulus Hall, 1879, Eleventh Indiana Rep., p. 266, is probably a Homo- 



crinus (?). 

 1880. P. anomalos Wetherby, Journ. Cincin. Soc. Nat. Hist. (July), p. 15, PI. 5, fig. 



6. Kaskaskia gr. Pulaski Co., Ky. This is one of the most perplexing 



species of this group. It agrees neither with Grapliiocrinus, nor Decado- 



crinus, nor ScapMocrinus, nor Eupachycrinus, and really shades into all 



of them. 

 1882. P. araclinaeformis Worthen, Bull, i. III. St. Mus. Nat. Hist., p. 13, PI. 28, fig. 



12: also Geol. Rep. Illinois, vii, p. 281, PI. 28, fig. 12. Keokuk limest. 



Warsaw, 111. 



P. Bockschii Geinitz. Only known to us from quotations. 



P. calyx Hall, 1879 (non De Koninck, 1853), is only defined from basal 



plates. Niagara gr. 

 1882. P. clytis Worthen, Bull. No. 1, 111. St. Mus. Nat. Hist., P. 16 (not P. clytis on 



p. 25); also Geol. Rep. 111., vii, p. 294, PI. 30, fig. 10. St. Louis limest. Monroe 



Co., 111. A very young specimen, as seen by the form of the brachials and 



arm joints j it probably had 10 arms in its adult state. 



