GENUS EUCALYPTOCRINUS. 321 



GENUS EUCALYPTOCRINUS (Goldfuss). 



This genus has usually been described as having five basal plates ; but 

 Dr. Troost, in his Memoir on, the Crinoidea, has described the genus as 

 having four basal or pelvic plates. 



In the study of the collections from Waldron, Indiana, in 1861-62, this 

 feature was fully ascertained, thus confirming the original observations of 

 Dr. Troost*. 



The basal plates of the species of this genus are usually small, and either 

 concealed in the basal cavity or covered by the column. 



The form and relations of these plates are shown in the accompanying 

 diagram ; while in the original specimen, both these and the lower part of 

 the first radial plates are covered by the column. On the smaller dia- 

 gram, fig. 2, the basal plates of E. ccelatus are given of the natural size, 

 showing also their relation with the first radial plates. 



This determination of the basal plates will remove the Genus EuCA- 

 LYPTOCRINUS from its present position among the Crinoidea which have 

 five basal plates, and bring it into association with Melocrinus. 



Fig. 1. 



Fm, 1, The basal and first radial plates of jEwcaZi/jsfomnws ccelatus : from the inside. 



Fig. 2. 



DD^ 



Fig. 2. Diagram of Eucaltptocrinus. 



* I end not at that time publish an account of this structure in my paper on the 

 Waldron fossils, wishing that it might first appear in the publication of Dr. Troost's 

 Memoir ; but since that has been delayed, I notice it in this place, giving Dr. Troost 

 the credit of the original discovery. 



[January, 1865.] 41 17 



