RHODOCRINID^. 233 



Infrabasals placed at the bottom of a concavity ; forming a penta- 

 gon, of which small portions are exposed beyond the column. Basals 

 smaller than the radials and without nodes or tubercles ; they rest wdthin 

 the lower concavity, except their extreme npper ends, w^hich bend slightly 

 upwards. Eadials large, forming a rim upon which the calyx rests ; their 

 tubercles quite long, rounded at the ends, and directed obliquely downward. 

 Costals comparatively large, their tubercles connected with one another, and 

 sometimes w^ith those of adjoining radials and interradials by obscure ridges. 

 Distichals one in the calyx, provided with a horse-shoe-shaped facet for the 

 reception of the free brachials. Arm openings elongate, facing laterally ; 

 structure of the arms unknown. First interradial followed by interbrachials 

 in succession of 2, 2, and two more between the arm openings. The anal 

 interradius has three plates in the second and succeeding rows, but the plates 

 are not formed into a ridge or placed in a straight line, their arrangement 

 being rather irregular. Interdistichals one, on a level with the arm openings. 

 Tegmen very small, flat, and of the plates only the ends of the tubercles vis- 

 ible from a side view ; the plates large and irregularly arranged. Anal open- 

 ing marginal. 



Horizon and Locality/. — Age of the Lower Burlington limestone. Lake 

 Valley, New Mexico. 



Types in the collection of Wachsmuth and Springer. 



RemarJcs. — This species, Avhich has the general habitus of certain forms 

 of GiWertsocrinus, differs from all other species of Rhodocnnus in the form of 

 its nodes, wdiich cover almost the whole flice of the plates. The largest 

 nodes occur on the radials, and not on the basals, those of the latter plates 

 being often wanting altogether. It also differs in the form and greater size 

 of the costals and distichals. 



GILBERTSOCRINUS Phillips. 



1836. Phillips; Geology of Yorkshire, Part II., p. 207. 



1841. MtJLLER ; Berlin. Acad. der. Wissenscli., p. 209. 



1849. D'Orbigny; Prodrome I., p. 155. 



1852. D'Orbigny ; Cours element.. Vol. II., p. 142. 



1865. Meek and Worteen ; Proceed. Acad. Nat. Sci. Ptiila., p. 166. 



1872. Hall; N. Y. State Mus. of Nat. Hist., Bull. I., Plate la and Plate VI. 



1873. Meek and W^orthen ; Geol. Rep. Illinois, Vol. V., p. 389. 



1875. Grenfell ; Proceed, of Bristol Naturalists' Soc, Vol. I., Part III., p. 483. 



Syn. OUacrinus Cumberland ; 1826, Appendix to Reliquiae Conservata, Plate D ; 1877, Waclismutli ; 

 Amer. Journ. Sci., Vol. XIV., p. 125 ; 1878, Zittel ; Handb. d. Palaeont., Vol. I., p. 376 ; 1881, 

 W. and Sp. ; Revision Palseocr., Part II., p. 213 ; and Proceed. Acad. Nat. Sci. Phila., p. 387; 



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