50 CIDARIS. 



Judging from the spines figured by Goldfuss, Agassiz, Roemer, and Cotteau, this 

 species must have had a wide European area of distribution, as its test or spines have been 

 collected in the Coral Rag of different parts of Germany, Switzerland, and France. 



History. — The history of this species has been given with so much detail in the 

 introductory remarks, that it is unnecessary to reproduce the facts under this section. 



Cidaris Smithii, Wright, nov. sp. PI. II, fig. I a, b, c, d, e ; PI. V, fig. 5 a, b, c, d, e. 



Test large, much inflated at the sides, and depressed at the poles ; ambulacral areas 

 flat, with two marginal rows of small granules, and two inner rows of microscopic granu- 

 lations ; poriferous zones wide, the pores separated by very thick septa ; inter-ambulacral 

 areas with ten primary tubercles in each row ; areolas oval, and deeply sunk ; scrobicular 

 granules not larger than the miliary granules j miliary zone wide and concave, and filled 

 with six or eight rows of nearly equal-sized miliary granulations ; mouth opening wide, 

 peristome pentagonal, jaws and teeth large and powerful ; primary spines long, slender, 

 and tapering ; surface of the stem with thick longitudinal ridges, from which stout 

 forward- directed processes proceed. 



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

 inches and three fourths of an inch. 



Description. — This noble urchin is a much rarer form than the preceding species, with 

 which, however, it is sometimes associated in the same beds of the Coralline Oolite in 

 Wiltshire and Yorkshire. As a distinct species, it has hitherto escaped the notice of 

 palaeontologists. 



The test is large, much inflated at the sides (PI. II, fig. ] b), and depressed at 

 both poles ; the ambulacral areas are slightly elevated, of moderate width, and gently 

 undulated ; they are widest at the equator, and diminish above and below ; they have 

 two marginal rows of small granules, which are alternately larger and smaller (fig. 1 c) ; 

 sometimes two of the smaller granules are interposed between every two of the larger 

 ones ; within these marginal rows are two rows of close-set, equal-sized, microscopic 

 granules, which disappear at the upper and lower parts of the areas. 



The poriferous zones are very superficial, and are nearly as wide as the areas ; the 

 pores are separated by thick septa, and the pairs of pores are directed obliquely upwards ; 

 the holes of the inner row are round, whilst those of the outer row are oblong or pyriform ; 

 the septa are slightly scooped out on their margins above and below, so that each pair of 

 pores, with its intervening partition, somewhat resembles the frame of a pair of spectacles, 



