1881.] NATURAL SCIENCES OF PHILADELPHIA. 387 



1861. Rhodoor. Wachsmuthi Hall. Desc. New Sp. Crin., p. 18. Lower Burlington 



limest. Burlington, Iowa. 

 1861. Bhodocr. Whitei Hall. Desc. New Sp. Grin., p. 9 ; Best. Journ. Nat. Hist., 



p. 324, Phot. Plates, 1875, PI. 6, figs. 19, 20, 21. 

 Var. barlingtonensis Hall. Desc. New Pal. Crin., 1861, p. 9; also Bost. 



Journ. Nat. Hist., p. .325. Lower Burlington limestone. Burlington, lowii. 

 1858. Bhodocr. Wortheni Hall. Geol. Rep. Iowa, i, pt. ii, p. 556, PI. 9, figs. 8 a, 



b, c. Lower Burlington limest. Burlington, Iowa. 



13. OLLACKINUS Cumberland. 



(PI. 18, fig. 2, and PI. 19, fig. 1.) 



1836. Cumberland. Appendix to Reliquiae Conservata. 



1877. Wachsmuth. Amer. Journ. Sci. and Arts, xiv, p. 135. 



1879. Wachsmuth and Springer. Proc. Acad. Nat. Sci. Phila , p. 261. 



1879. Zittel. Handb. der Palaeont, i, p. 375. 



Syn. Gilbertsocrinus Phill. Greol. Yorkshire, pt. ii, p. 207 ; 

 d'Orbigny, 1850, Prodr. de Paleont., i, p. 155 ; Meek and Worth., 

 1866, Geol. Rep. 111. ii, p. 217. 

 Syn. Goniasteroidocrinus Lyon and Casseday. Amer. Joiirn. Sci. 

 and Arts, vol. 28 (ser. 2), p. 233 ; Meek and Worthen, 1869 (Sub- 

 genus of Gilbertsocrinus), Proc. Acad. Nat. Sci. Phila., p. 7o and 

 1873, Geol. Rep. 111., v, p. 389. 

 Syn. Trematocrinus Hall. Supp. Geol. Rep. Iowa, p. 70 ; Meek 



and Worthen, 1860, Proc. Acad. Nat. Sci. Phila., p. 383. 

 Syn. Rhodocrinus (in part) de Koninck and Lehon. Recher. Crin. 

 Carb. Belg., p. 104. 



The form under consideration was first made known by 

 Cumberland in the Appendix to his Reliquiae Conservata, 1826, 

 under the name Ollacrinus. He published no generic diagnosis 

 nor specific name, but gave excellent figures, by which the type 

 represented can be easily identified. It is characterized by a 

 pentamerous figure, concave base, flat vault, excentric anal opening, 

 spiniferous first radials, and by large oval-shaped interradial and 

 anal spaces, with numerous plates. There are two sets of openings 

 in the brachial regions, the largest supported b}' the secondary 

 radials, and the others located nearly above thenj, being smaller, 

 and perforated directly through the centre of pairs of plates in 

 the margin of the vault. 



In 1836, Phillips, in the Geology of Yorkshire, proposed the 

 genus Gilbertsocrinus, and included in it Cumberland's type, 

 which he described as G. calcaratui>, and two other species. 

 His figures are fairly good, but his descriptions are ver}- meagre, 

 and show no essential difference from Rhodocrinus. Thev contain 



