PLATE XXVII. 



Clypei from the Inferior Oolite. 



1 a. Clypeus altus, M'Coy, p. 366. Upper surface, natural size. 

 h. Under surface of the same test, natural size. 



c. Lateral view of ditto, showing the convexity of the dorsal surface, and the deep 



undulations of the border. 



d. Posterior view, showing the structure of the inter-ambulacruni ; the length, and 



narrowness of the anal valley, and the shape of the vent. 



e. Ambulacral area, zones, and inter-anibulacral plates, magnified four times. 



/. Apical disc, with the large raadreporiforui body, small ocular plates, and posterior 

 complementary plates, magnitied live times. 



2 a. Clypeus Michelini, Wright, p. 369. Upper surface, natural size. 

 h. Lateral view of the same test, natural size. 



c. Ambulacral area, zones, and inter-ambulacral plates, magnified five times. 



This is a rare urchin, on a slab of Inferior Oolite limestone, from Whitwell, Yorkshire, 

 where it was found associated with Stomechinus germinans, Phillips. 



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