1881.] NATURAL SCIENCES OF PHILADELPHIA. 379 



up, of two series of wide and short interlocliing pieces. Arm 

 furrows wide and deep ; pinnules present, but their exact form 

 not known. 



Column round ; central canal small. 



Geological Position^ etc. — Lyriocrinus occurs only in rocks at 

 the age of the Niagara limestone of America. 



We recognize only two species ; L. sculptilis Hall, a third 

 species is described from mere casts, and very doubtful. 



1343. Lyriocrinus dactylus Hall. (Marsupiocrinites dactylus) Type of the genus. 



Geol. Rep. 4th Distr. N. York, p. 114 : Hnll, 1 852, Lyriocr. dactylus, Paleont. 



N. Y., PI. 44, figs. 1 a-g : Pictet, 1857, Traite de Paleont., iv, p. 329, P). 101, 



fig. 12. Niagara gr. Lockport, N. York. 

 1S63. Lyriocr. melissa Hall. (Rhodocr. melissa) Trans. Albany Inst., p. 198; also 



2Sth Rep. N. Y. St. Cab. Nat. Hist. (ed. ii), p. 139, PI. 15, figs. 18-22. 



Niigaragr. Waldron, Ind. 



9. RIPIDOCRINUS Beyrich. 



1879. Zittel. Handb. der Palaeont., i, p. 377. 



Syn. Bhodocrinus Goldfuss. Petrefact. Germ., 1, p. 211 ; Agassiz, 

 1835, Mem. Soc. Neuchat., 1, p. 196 ; Muller, 1841, Verhaudl. d. 

 Berl. Akad., i ; Roemer, Verb. Naturh. Verein f. Rheinl., viii, p. 

 358 ; and 1855, Lethaea Geogn., ii, p. 241 ; Pictet, 1857, Traite de 

 Paleont., iv, p. 314 ; Schultze, 1867, Echin. Eifl. Kalk, p. 53. 



Beyrich's name Ripidocrinus, so far as we now know, was first 

 published by Zittel to include Rhodocr. crenatus Goldf. This 

 species differs very materially in the arm structure from Rhodo- 

 crinus as established \>y Miller. In the general form of the body 

 and the arrangement of the plates, it resembles Lyriocrinus Hall, 

 but the arm structure separates them widely. 



Generic Diagnosis. — Calyx cup- or urn-shaped, sometimes 

 subglobose, lower portions more or less truncate, the basals 

 spread out horizontally from the column ; plates heavj", highly 

 ornamented ; symmetry equilateral. Body extended into free 

 raj'^s with lateral arms. 



TJnderbasals five, closel3" anchylosed, small, forming a pentagon, 

 deepl}' depressed, and gene rail}' hidden from view b}' the large 

 column ; central perforation large, pentalobate. 



Basals five, equal, irregularly hexagonal, the lower side in line 

 with the sides of the inner pentagon ; the lower lateral sides, by 

 which the plates are united, extremely short ; upper lateral 

 margins, which enclose the first radials, unusually long ; upper 



