INVERTEBRATES. 501 



ECHINODERMATA. 



Genus ETTCALYPTOCRINUS, Goldf. 



EucALTPTOCRtNUS magnus, Worthen. 



PI. 25, Fig. 3. 



Body above the medium size, broadly discoidal below the arm bases, 

 forming a shallow cup. Base rather deeply impressed, basal plates small 

 and concealed in the depression for the reception of the first columnar 

 facet. First radial plates large, hexagonal, wider than high, .with the 

 upper lateral angles truncated for the reception of the first interradials, 

 and the lower angle depressed into the basal cavity ; second radials quad- 

 rangular, wider than high, but varying in their proportions ; third radials 

 hexagonal, a little wider than high, and supporting a rather high and 

 narrow fourth radial or supra-radial, the upper portion of which turns 

 abruptly upward for the support of an arm plate. First interradial 

 quite large, longer than wide, with ten distinct angles, and supporting on 

 its upper angles two long hexagonal pieces that extend upward nearly as 

 high as the fourth radials, and like them curve upward at their upper 

 extremities. On each side of these pieces there are four other plates, 

 the lowest and largest being pentagonal and resting against one 

 of the lateral angles of the first interradial, and giving support to a 

 smaller hexagonal plate above, that in its turn supports two small tri- 

 angular pieces on its upper angles. Arms and column unknown. 



This large and fine species is so unlike any of the forms usually met 

 with from this horizon that a comparison seems hardly necessary. Pos- 

 sibly it may be included in Dr. Teoost's catalogue of the crinoids of 

 Tennessee, published in 1850, in the Proceed. Amer. Asso., Cambridge 

 meeting, p. 60 ; but as no descriptions of the species there catalogued 

 have ever been published so far as is known, this point can only be 

 decided by a comparison of specimens. 



Position and locality : Wayne county, Tennessee, in the red limestone 

 at the base of the Upper Silurian. 



