CRINOID GENUS SCYPHOCRINUS 25 



of the genus is carried down into undoubted Silurian, it may be that this 

 correlation should await further revision by the stratigraphists. Although they 

 figure on plate 44, figure 3, a specimen of 5". subornatns with a part of a 

 Lobolithus in contact, Messrs. Waagen and Jahn nowhere intimate the possi- 

 bility of their being parts of the same organism. But in 1904, in a letter quoted 

 in Schuchert's paper (p. 259), Professor Jahn states that "certain Loboliths 

 belong to Scyphocrinus," he having observed them " connected by long columns 

 to Scyphocrinus calices." 



I have given the foregoing abridgement of Waagen and Jahn's definitions 

 of the Bohemian species for the purpose of comparison with the American 

 species, in view of the remarkable parallelism that exists between them. 



In this country there seem to be at least eight species based upon the 

 characters shown by the calyx, from four widely separated areas — all of 

 Helderbergian age; one from the lower, the Keyser beds, and the others from 

 the higher Linden, Bailey, and Haragan beds, one of which, however, goes down 

 into the Niagaran. They are divisible into two well-marked groups, distin- 

 guished by radically different types of calyx. The Missouri form, the only one 

 of which the arms are fully known, is in size, surface ornament, structural 

 details, and general habitus so remarkably like the leading Bohemian species 

 that no reliable differentiating characters can be found in the fossil state. 

 Most of the others are well characterized. 



A further remarkable modification within the limits of the genus is seen 

 in the presence of articulated spines, as shown in 5". spinifer. 



The stratigraphic range of Scyphocrinus is considerable, extending from 

 the Decatur formation of the Niagaran to the close of the Helderbergian in 

 the Tennessee area. S. mutabilis occurs in Perry County in a bed of yellow, 

 granular, crinoidal limestone referred to the Decatur limestone (the highest 

 member of the Niagaran), associated with the genera Clonocrinus, Desmido- 

 crinus, Gazacrinus, Eucalyptocrinus, Marsipocrinus, Lecanocrinus, and Piso- 

 crinus; and another indistinct species along with frequent Camarocrinus has 

 been found in a hard grey limestone underlying the yellowish layers. 



Hence in these beds at the top of the Niagaran, intermingled with its char- 

 acteristic species, Scyphocrinus begins and from there continues throughout 

 the Linden to its highest beds in the northern part of Benton County, where 

 it is associated with Devonian species quite different from those of the other 

 Linden beds. Among these Devonian forms I have recently obtained a well- 

 marked specimen of Phimocrinus, the ancestral form of Synbathocrinus, a 

 genus not hitherto seen in America; and numerous weathered fragments 

 indicate the presence of a form like Stereocrinus, which would carry the Dola- 

 tocrinites a stage lower in the stratigraphic scale than has been hitherto known. 



