26 



SMITHSONIAN INSTITUTION 



The correlation of the different local formations containing Scyphocrinus, 

 according to the latest determination of the U. S. Geological Survey, may be 

 stated as follows: 





Tennessee 



Missouri 



Oklahoma 



West Virginia 



« < 

 Q 



S 



•2 

 'Sj 



Linden formation 

 (Ross Is. at base) 



Bailey Is. 



Haragan Is. 



Keyser Is. 



< 

 p 



Niagaran 



Decatur Is. 









It is a question how to deal with the described species of Camarocrinus, 

 now that it is certain that they all belong to the genus Scyphocrinus. The 

 characters on which they are based, namely, the form and proportions of the 

 bulbous root and the different conditions of its external surface, are in my 

 opinion of little or no diagnostic value. The root in Paleozoic crinoids, when 

 it exists, is a generalized structure, usually not marked by specific differences 

 (even the stem as a whole having by no means the taxonomic value which it 

 has in the Recent crinoids) ; while as to surface characters, the differences 

 hitherto noted are largely due to chemical action and the effect of weathering. 

 This is well shown among specimens in my collection from the same locality. 

 Those which are apparently little altered from their original condition have 

 a smooth surface, composed of undifferentiated small plates, as shown in Hall's 

 figure I of plate 36, in the 28th Report of the New York State Cabinet; if the 

 calcareous surface of these has been dissolved and the underlying structures 

 replaced by silica, various sorts of rugosities, more or less regular, will often 

 appear; e. g., as in Schuchert's var. stellifer (op. cit., pi. 40, fig. a; pi. 41, fig. b). 



The form and number of the lobes into which the bulbs are divided are 

 variable, and as specific characters these are of no importance whatever. 

 Usually the chambers developed from the root branches are represented by 

 more or less protuberant, unequal lobes. The primary number is four, to 

 which others may be added to a total of about 11, as already explained; and 

 exceptionally the number is reduced to three. In case of five lobes, which is 

 the most frequent variation, the added lobe is usually much smaller than the 

 original four; a symmetrically quinquelobate bulb is the exception. In many 

 cases the external lobing is quite obscure, so that the bulb appears almost 

 regularly spheroidal. These facts are conclusively shown by the series of 70 

 finely preserved Camarocrini from the clay bed in Hardin County, Tennessee, 

 already mentioned. They are all from a single colony, found in the place of 



