8 Cincinnati Society of Natural History. 



roneously done, those species having the constructiou of Dichocrinus.^ 

 and differing- in every essential particular from Fterotocritms. None 

 of the species present any evidence of scul[)ture or ornamentation ; nor 

 do any of the mau}^ other fine Crinoids found associated with them. It 

 might be supposed that this was the result of erosion, wei-e it not for 

 the fact that the many beautiful species of Chmtetes, Polypora, Fisfuli- 

 pora., Septojiora, etc., associated with them, have all their most delicate 

 structure perfectly preserved. It must then be inferred that the Cri- 

 noidea of this group were plain species. The true formula of the 

 genus is as follows : Basals, 2 ; radials, 1st series, 5 ; radials, 2d 

 series, 10 ; radials, 3d series, 20 ; brachials, 3 or 4, x 20 ; axillaries 

 or interbrachial rays, 5 ; anal plate, 1 or more (?) ; arms, 20 ; column 

 small and round ; exterior without ornamentation. Geological position : 

 upper half of the Kaskaskia Group of the Sub-carboniferous, in sandy 

 shales, Pulaski Co., Ky. The wide variation exhibited in the form of 

 the different species of this remarkable Crinoid ; the inconstant character 

 of its plates; the different arrangement of the vault pieces at the apex; 

 the strange and widely varying^forms of the rays, are each evidences of 

 the impossibility of arranging a genei'ic formula that shall include all 

 cases; but that given is as near perfect as can be. The almost entire 

 anchylosis of the first and second radials in old individuals ma}' easil}- 

 lead one astray who does not study sliced specimens; while the varying 

 form of the rays found, and not yet referred to discovered species, 

 shows that there are large numbers of forms as yet unknown. It is 

 plain that its nearest alliance is with Eucalyptocrinus., which has four 

 basals, or a second division of those of Pterotocrinus and Dichocrinus. 

 I am satisfied, however, that all classification of the Crinoidea, based 

 merely upon the arrangement of the pelvic plates, will soon be super- 

 ceded by the more rational one of the relationship of internal structure. 



DESCBIPTION.s OF NEW GENERA AND SPECIES OF 



FOSSILS FROM THE LOWER SILURIAN 



ABO UT CINC INN A TI 



By E. O. Ulrich. 



In giving the formations in which the following species occur, the 

 terms Utica shale and Hudson River Group are used instead of Cin- 

 cinnati Group. The term Cincinnati Group was mainly established 

 l)y Messrs. JNIeek and Worthen, on account of the supposed absence, 

 in the Cincinnati exposures, of the Utica shale. The rocks exposed at 

 High Bridge, Lexington, and many other localities in Kentucky, are 



