302 PROCEEDINGS OF THE ACADEMY OF [1881. 



1879. Zittel. Ilandb. der Palteontologie, i, p. 368. 



Syn. Actinocrinus Miller, 1821 (in part). Hist. Crinoidea, p. 116. 

 Syn. Actinocrinus Phillips, 1839. Murchis. Silur. Syst., p. 57. 

 Syn. Trochocrinites Portlock, 1848. Geol. of Londonderry, p. 345. 

 Syn. Pradocrimis De Verneuil, 1850. Bull. Soc. Geol. France (ser. 



ii), vol. vii, p. 184. 

 Syn. Geocrinus d'Orbigny, 1850. Prodr. de Paleont., i, p. 46. 

 Syn. Saccoci'imis Troost, 1850. List. Grin. Tenn. 

 Syn. Saccocrinus Hall, 1852. Paleont. New York, ii, p. 205. 

 Syn. Pyxidocrinus Miiller (in part), 1857. Neue Eclun, Eifel Kalk, 



p. 253. 

 Syn. (?) Trochocrinites Pander, 1858. Helmerson's Geol. Bermerk. 



auf einer Reisein Schweden, etc., p. 20. 

 Syn. Saccocrinus Roenier, 1860. Silur. Fauna West. Tenn., p. 42. 

 Syn. Actinocr. (Megistocrinus) Hall, 1861. Bost. Journ. Nat. Hist., 



p. 271. 

 Syn. Actinocr. {Pradocrinus) Meek and Worth., 1861. Proc. Acad. 



Nat. Sci. Phila., p. 133. 

 Syn. Actinocrinus Hall, 1863. Trans. Albany Inst., v, p. 196. 

 Syn. Megistocrinus Winchell and Marcy, 1865 (not Ow. and Shum.). 



Mem. Bost. Soc. Nat. Hist., 1, p. 87. 

 Syn. Saccocrinus Meek and Worth., 1869. Geol. Rep. 111., iii, 



p. 347. 

 .Syn. Actinocr. {Saccocrinus) Meek and Worth., 1869. Geol. Rep. 

 ' 111., iii, p. 470. 

 Syn. Megistocr. {Saccocrinus) Meek and Worth., 1873. Geol. Rep. 



111., vol. V, p. 397. 

 Syn. Actinocrinus Angelin, 1878 (in part). Iconogr. Grin. Suec, 



p. 6. 

 Syn, Saccocrinus S. A. Miller. Journ. Cincin. Soc. Nat. Hist. 



(July No.). 



Austin's definition of Periechocrinus is not so clear as might 

 be wished, but sufficiently distinct to imply that he described a 

 group of Crinoids of which Miller's Actinocrinus moniliformis is 

 the type. None of Austin's species were figured ; the first, F. 

 articulosus^ is but little known, the second, P. costatus has been 

 regarded a synonym of Actinocr. moniliformis^ while the third, 

 P. glohulosus, has not been defined. The species are character- 

 ized by their elongate sack-like form, the thinness of their body 

 plates, the exceedingly high radials, the conspicuous elevated 

 ridges along the radials, the large interradial and interaxillary 

 spaces, the wide anal area with a plate in line with the first 

 radials, and the large, slender, more or less branching arms. This 

 includes the American species for which Troost and Hall proposed 

 the genus Saccocrinus. 



