164 HEMIPEDINA. 



Mr. Bean ever saw after collecting many years from the Coralline Oolite of Malton, York- 

 shire, and fragment (fig. 1 b), is the only portion showing the external surface of the 

 plates I have obtained from the Coral Rag of Calne, Wilts ; from this locality, however, 

 I have seen the interior of a large Hemipedina which was upwards of three inches in 

 diameter, having the jaws " in situ," but as the external surface of all the plates was con- 

 cealed, the species was indeterminable, it most probably however belonged to this species, 

 as the figure of the plates was the same as those in (fig. 1 b, c). 



Hemipedina tuberculosa, Wright. PI. XI, fig. 2 a, b, c, d, e,f. 



Hemipedina tuberculosa. Wright, Annals and Magazine of Natural History, 2nd series, 



vol. xvi, p. 99. 



— — Woodward, Memoirs of the Geological Survey, Decade v, 



" Notes on Echinopsis." 



— — Desor, Synopsis des Echinides Fossiles, p. 60. 



Test hemispherical, depressed ; ambulacral areas narrow, with two rows of semi- 

 tubercles at the base, which extend as high as the equator ; upper part of the areas with 

 two rows of very small marginal granules ; interambulacral areas with two rows of primary 

 tubercles set on prominent bosses, the areolas surrounded by circles of coarse scrobicular 

 granules ; between the peristome and the equator there are two rows of small secondary 

 tubercles on the zonal side of the plates, and several at the base of the rows ; the miliary 

 zone is wide, and covered with coarse granules, the sutural lines are naked above ; mouth 

 opening large, the peristome very unequally lobed, the ambulacral being double the size 

 of the inter-ambulacral lobes ; anal opening large ; spines moderately stout and covered 

 with longitudinal lines. 



Dimensions. — Height, seven tenths of an inch ; transverse diameter, one inch and one 

 fifth of an inch. 



Description. — This new and beautiful urchin was only discovered a few months 

 ago in the Coral Rag of Wiltshire. The original type specimen, belonging to the British 

 Museum, has so much of the matrix adhering to its upper surface that its true form is 

 concealed ; the discovery, however, of the fine specimen I have figured, now enables me 

 to give very full details of its structure, including even the spines. 



The ambulacral areas are narrow ; their basal half is enlarged, and filled with two rows 

 of semi-tubercles gradually increasing in size from the peristome to the uppermost tubercle 

 (fig. 2 b, c, d), like the semi-tubercles of the same region in the genus Hemicidaris ; there 

 are eight tubercles in each row (fig. 2 c) which alternate with only a solitary granule at 



