FROM THE CORAL RAG. 219 



Affinities and differences. — This species most nearly resembles Stomechinus gyratus, hxxt 

 is distinguished from it by the absence of the naked median depressions in the inter- 

 ambulacral areas, which gives such a remarkable lobed character to the surface of its test ; 

 by the absence of the circles of granulations around the base of the tubercles ; and the 

 naked appearance which the surface of the plates presents, in consequence of the almost 

 total absence of this granular ornamentation, and which is expressed by its specific 

 name nudus. 



Locality and Stratigram Ideal position. — This Echinite was collected in Wiltshire, but 

 I have not been able to ascertain the correct locality ; it appears to have been obtained from 

 the Coral Rag, although this is not certain. 



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