RHODOCRINID^. 261 



Remarlcs. — Rhaphanocrinus sculptus was described as monocyclic, and 

 referred by S. A. Miller to Glyptocrinus. The infrabasals are only seen 

 as small dots around the column. The species is readily distinguished from 

 allied forms by having knife-like ridges upon the fixed brachials 3 while the 

 back of the free brachials is perfectly round. 



LYRIOCRINUS Hall. 



1852. Hall; Geol. Rep. N. Y, Palfeoiitology, Yol. II., p. 197. 



1857. PiCTET ; Traite de Paleont., Vol. IV., p. 329. 



1862. DuJARDiN and Hupe ; Hist. Natur. des Zooph. Ecliinod., p. 149, 



1866. Shumaud ; Trans. Acad. Sci. St. Louis, Vol. II., p. 379. 



1867. Hall; 20tli Rep. N. Y. State Cab. Nat. Hist., p. 325. 



1879. Hall; 28tli Rep. N. Y. State Mus. Nat. Hist. (ed. 2), p. 189. 



1881. W. and Sp. ; Revision Palseocr., Part II., p. 203 (Proceed. Acad. Nat. Sci. Phila., p. 377). 



1881. Hall; llth Ann. Rep. Indiana by Collet, p. 269. 



1889. S. A. Miller; North Amer. Geol. and Paleont., p. 258. 



Syn. Marsupiocrinus (not Phillips) Hall ; 1843, Geol. 4th Distr. New York, p. 114. 



Syn. Rhodocrinus (not Miller) Hall, 1863; Trans. Albany Inst., p. 198. 



Calyx depressed-globose^ more or less flattened to the middle of the 

 radials; symmetry almost perfectly pentamerous; plates heavy, their surfaces 

 smooth or finely granular ; ventral disk not rising above the dorsal cup ; arm 

 openings directed upwards, placed at the upper margin of the disk. Infra- 

 basals fiYQ, very small, abruptly and deeply depressed and concealed by the 

 column. Basals five, of uniform size, either all hexagonal and supporting 

 upon the truncate upper face the first interradial plate ; or quite frequently 

 one or more of them hexagonal, and angular at the top. Costals two ; large. 

 Two of the distichals enclosed in the calyx. Arms two to the ray, rising in 

 a straight line with the sides of the calyx ; simple, strong, biserial, two of the 

 interlocking plates frequently in the calyx. Interbrachials four, in three 

 rows: 1, 2, 1. Anal side generally not distinct^ but exceptionally it has 

 a special anal plate in the second row. Disk flat, somewhat depressed in the 

 interradial regions ; composed of a great number of slightly convex, dehcate 

 pieces, and well defined orals. Anus subcentral, probably at the end of a 

 small tube. 



Column of less than medium size, round ; axial canal small. 



Distribution. — Upper Silurian. America and Europe. 



Ti/pe of the genus : Lyriocriniis dactt/lus Hall. 



Eemarhs. — The name Lyriocriniis was proposed for a species from the 

 Niagara group of Lockport, which had been described under Marsupiocrinus^ 



