300 PROCEEDINGS OF THE AMERICAN ACADEMY 



P. Shumardianus, Hall, Iowa, Vol. 1, p. 532, PI. 8, fig. 5. Sub- 

 carboniferous. Burlington limestone. 



P. SUBSPINOSUS, Hall, Iowa, Vol. 1, p. 536, PI. 8, fig. 9, 10. Sub- 

 carboniferoiis. Burlington limestone. 



P. TUBEROSUS, Hall, Iowa, Vol. 1, p. 534, PI. 8, fig. 7, a, b. Sub- 

 carboniferous. Burlington limestone. 



P. TRUNCATULUS, Hall, lowa, Vol. 1, p. 538, Diagram. Subcar- 

 boniferous. Burlington limestone. 



P. TRUNCATUS, Hall, lowa, Vol. 1, p. 537, Diagram. Subcarbon- 

 , iferous. Burlington limestone. 



P. WoRTHENi, Hall, Iowa, Vol. 1, p. 530, PI. 8, fig. 4. Subcar- 

 boniferous. Bui'lington limestone. 



P. Yandelli, Owen and Sliumard, Journ. Acad. Nat- Sci. Philad. ; 

 Geol. Survey of Wisconsin, Iowa, and Minnesota, p. 587, 

 PI. 5 A, fig. 6, a, b. Subcarboniferous. Burlington, Iowa. 



PLEUROCYSTITES, Billings, 1854, Canad. Journ., Vol. 2, p. 250 ; 



Survey Rej). 1857, p. 284. Silurian. Lower Silurian. 

 » P. Anticostiensis, Billings, Geol. Survey of Canada, Palteont., 



Dec. III. p. 52, PI. 1, fig. 3. Silurian. Hudson River group. 

 P. ELEGANS, Billings, Geol. Survey of Canada, Palaeont., Dec. HI. 



p. 51, PI. 2, fig. 2, a-d. Siluria7i. Trenton limestone. 

 P. EXORNATUS, BiUiugs, Geol. Survey of Canada, Palajont., Dec. 



III. p. 52. Silurian. Trenton limestone. 

 P. FiLiTEXTUS, BiUings, Geol. Survey of Canada, Palteont., Dec. 



III. p. 50, PI. 2, fig. 1, a, b. Silurian. Trenton limestone. 

 P. ROBUSTUS, Billings, Geol. Survey of Canada, Palnaont., Dec. 



III. p. 49, PI. 1, fig. 2, a. Silurian. Trenton limestone. 

 P. SQUAMOsus, Billings, Geol. Survey of Canada, Pala^ont., Dec. 



in. p. 49, PI. 1, fig. 1, a-d. Silurian. Trenton lime- 

 stone. 



POTERIOCRINUS, Miller, 1821. 



P. ALTERNATUS, Hall, PaL«ont. N. York, Vol. 1, 1847, p. 83, PI. 

 28, fig. 1, a - f. Silurian. Trenton limestone. 



P. CALYCULUS, Hall, Iowa, Vol. 1, p. 553, PL 9, fig. 6, a, c. Sub- 

 carboniferous. Burlington limestone. 



P. GRACILIS, Hall, Palajont. N. York, Vol. 1, 1847, p. 84, PI. 28, 

 fig. 2, a - f. Silurian. Trenton limestone. 



