304 PROCEEDIISrGS OF THE AMERICAN ACADEMY 



THYSANOCRINUS, Hall, 1852. 



T. ACULEATUS, Hall, Palaeont. N. York, Vol. 2, p. 190, PI. 42, fig. 



3, a - cl. Silurian. Niagara group. 



T. CANALICULATUS, Hall, Pala^ont. N. York, Vol. 2, p. 189, PI. 42, 



fig. 2, a - d. Silurian. Niagara group. 

 T. iMMATURUS, Hall, Palaeont. N. York, Vol. 2, p. 191, PI. 42, fig. 



4, a - f. Silurian. Niagara group. . 



T. LiLiiFORJUS, Hall, 1. c, fig. 1, a-f. Silurian. Niagara group. 



VASOCRINUS, Lyon, 1857. 



V. SCULPTUS, Lyon, Geol. Survey of Kentucky, Vol. 3, p. 486, PI. 



4, fig. 3, b - e. Devonian. Beargrass Creek, Kentucky. 

 V. VALENS, Lyon, 1. c. fig. 3, 3 a. Devonian. Beargrass Creek, 



Kentucky. 



ZEACRINUS, Troost, MSS. (Hall).* 



Z. DEPRESsus, Troost, MSS.; Hall, Iowa, Vol. 2, p. 546. Siib- 

 carhoniferous. 



Z. ELEGANS, Hall, Iowa, Vol. 1, p. 547, PI. 9, fig. 12. Suhcarhon- 

 iferous. 



Z. iNTERMEDius, Hall, lowa, Vol. 1, p. 681, PI. 25, fig. 4. Suhcar- 

 honiferous. Kaskaskia limestone. 



Z. MAGNOLi^FORMis, Troost, MSS.; Hall, I.e. pp. 684, 545, 544. 

 Subcarboniferous. Pentremital limestone, Tennessee. 



Z. MANiFORMis, Hall, 1. c. p. 682, PI. 25, fig. 8. Poteriocrinus 

 maniformis, Yandell and Shumard, Contrib., p. 24, PI. 1, 

 fig. 2. Cyatliocrinus maniformis, Yandell and Shumard, 

 Contributions. C. gracilis, Troost, Cat. Subcarhoniferous. 

 Kaskaskia limestone, Illinois ; Ai'chimedes limestone, Ken- 

 tucky. 



Z. RAMOSUS, Hall, Iowa, Vol. 1, p. 548, PI. 9, fig. 3. Subcarbon- 

 iferous. Burlington limestone. 



Z. WoRTHENi, Hall, Iowa, Vol. 1, pp. 545, 683, with diagram. 

 Subcarhoniferous. Kaskaskia limestone. 



* " This genus begins its existence, so far as known, in the Burlington limestone, 

 and continues to the Chester limestone, becoming far more abundant and extrava- 

 gant in its forms in the latter period." — Hall. 



