FROM THE INFERIOR OOLITE. 155 



The base is flattened, but the mouth opening is unfortunately concealed in the only 

 two specimens I have found. 



Affinities and differences. — I regarded this urchin, at first sight, as a young form of 

 H. tetragramma, but the spaced-out an'angement of the ambulacral tubercles, the inflation 

 of the sides of the test, and the presence of only two rows of tubercles in the inter- 

 ambulacra, show that it is quite distinct from that species. It is so entirely difierent from 

 H. perforatus and H. BaJceri, that it cannot be mistaken for either of them. 



Locality and Stratigraphical position. — I collected this urchin in the Pea Grit at 

 Crickley Hill, with the former. It must be rare, as I only know two examples of the 

 species, which I dedicate to my friend G. R. Waterhouse, Esq., F.Z.S., of the British 

 Museum, well known for his valuable contributions to zoological literature, and by the 

 kindness and urbanity of his manner to all who seek information in that department 

 of the great national collection committed to his care. 



Hemipedina Bonei, Wright. PL X, fig. 5 a, h, c, d. 



Hemipedina Bonei. Wright, Annals and Magazine of Natural History, 2d series, vol. xvi, 



p. 98. 

 — — Woodward, Memoirs of the Geological Survey, Decade v, " notes on 



Echinopsis." 



Test small, pentagonal, depressed ; ambulacral areas with two marginal rows of 

 close-set tubercles ; inter-ambulacral areas with two entire central rows, and four shorter 

 lateral rows of tubercles, which extend only to the equator ; the tubercles of both areas are 

 small and nearly of the same size ; base concave ; mouth opening of moderate width ; 

 peristome nearly equally decagonal. 



Dimensions. — Height, seven twentieths of an inch ; transverse diameter, eight tenths 

 of an inch. 



Description. — This small pentagonal depressed urchin has the minute tubercles of both 

 areas nearly of the same size (fig. b b, c) ; the ambulacral areas are about one third 

 the width of the inter-ambulacral ; they have two rows of tubercles, from eighteen to 

 twenty in each row, set on the margin of the areas (fig. 5 c, d), with incomplete circlets 

 of small granules surrounding them (fig, 5 d), except on their zonal side, where 

 they are absent ; the poriferous zones are narrow, straight, and distinctly unigeminal 



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