GENUS EUCALYPTOCRINUS. 323 



the genus ; but above this the cavity appears to have been larger, and 

 shows no marks of the axillary plates, as usual in the dome of EuCA- 



LYPTOCRINUS. 



Formation and locality. In limestone of the age of the Niagara group 

 at Waukesha and Racine, Wisconsin. 



EUCALYPTOCRINUS CRASSUS. 



Eucalyptocrinus crassus : Hall, Transactions of the Albany Institute, Vol. v. 1863. 



Specimens which are casts of the interior and impressions of the exterior, 

 present the general aspect of this species. It is extremely variable in form. 

 Sometimes it is regularly turbinate and convex on the sides ; other speci- 

 mens are extremely elongate and sometimes abnormal in their development, 

 having the supraradial plates united at their lateral margins, and the 

 second interradials with the j&rst axillary plate resting upon their upper 

 sloping sides, instead of the truncated upper face of the interradial and 

 third radial plates. This variation sometimes extends only to one or two of 

 the plates, and sometimes, as far as can be seen, to all the plates of these 

 series. 



Formation and locality. In the limestone of the Niagara group at 

 Racine, Wisconsin. 



EUCALYPTOCRINUS OBCONICUS (n.s.). 



Body small, reversed conical : base narrowly rounded or obtusely pointed ; 

 basal plates small and curving upwards. First radial plates compara- 

 tively large ; the second and third smaller. The two supraradial plates 

 join at the lateral margins, and the narrow interbrachial rests upon 

 them, and does not truncate the third radial. 

 First interradial plate large, narrowly truncate above. 



This species occurring in several specimens is a remarkable form of 

 Eucalyptocrinus, being much more slender than any other species of 

 the genus known to me ; and presenting the peculiar relations of the inter- 

 brachial plates, which are elevated to a higher position than they occupy 

 in the normal structure of the genus. 



The position of the interbrachial plates, which appear to be uniform in 

 this species, is sometimes observed in specimens of E. crassus. 



Formation and locality. In the limestone of the Niagara group at 

 Racine, Wisconsin. 



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