164 Dr. T. Wright on neiu Species of Echinodermata 



parison of several individuals of our fossil with a typical spe- 

 cimen of Goldfuss's species, kindly sent us by our friend Dr. 

 Iloemer of Bonn, which he had identified with the original 

 C. elegans in the Bonn Museum now under his care, has con- 

 vinced us of their distinctness. The test of our Urchin is 

 circular and much depressed from the great flattening of both 

 poles ; the ambulacral areas are narrow and slightly flexuous, 

 and have two rows of small marginal granules set nearly op- 

 posite to each other throughout the areas. The poriferous 

 avenues are much depressed, and the pairs of pedal pores are 

 disposed in a single file. The interambulacral areas are about 

 five times the width of the ambulacral, and have two rows of 

 primary tubercles of moderate size, with from five to six in each 

 row. The mammillary eminences on which the tubercles are 

 supported are surrounded by areolas deeply excavated out of the 

 substance of the test plates ; the margin bounding the areolas is 

 raised into a ridge on which a distinct row of close-set granules is 

 disposed, so that each tubercle is thereby separated from its fellow; 

 the elevation of the marginal ridges produces a zigzag depression 

 down the centre of the areas, which is covered with a small 

 close-set granulation. The mouth-opening is small and circular, 

 and lies in a slight depression ; the apical disc is absent in all 

 the specimens that have yet been found. The crenulations on 

 the mammse are small, but distinct, and the tubercles are of 

 moderate size and not deeply perforated. 



Affinities and differences. — This Urchin has many affinities with 

 C. coronata, Goldf., and C.propinqua, Miinst., and has been cata- 

 logued as the former by some authors ; it is therefore important 

 that we should point out the diagnostic characters by which it is 

 distinguished from them. In both these corallian forms the am- 

 bulacral areas have four rows of granules, whilst in C. Bouchardii 

 there are only two rows. From C. propinqua and C. coronata 

 it is further distinguished by having more rows of primary 

 tubercles in the interambulacral areas, in having the areolas 

 smaller and more deeply sunk, the tubercles proportionately 

 smaller, and the marginal circle of granules smaller and set 

 closer together. With C. marginata, Goldf., it has some affinity 

 in the excavated style of its areolar spaces, but it is distinguished 

 from this beautiful form in having the tubercles smaller and 

 more numerous. In C. marginata the ambulacral areas moreover 

 are broader and more prominent, and they support four rows of 

 small granules, whilst in C. Bouchardii there are only two. With 

 C. eleganSjGoldt, it has no resemblance whatever; it belongs there- 

 fore to a different group of Cidarites than these foreign corallian 

 forms. From C. Fowleri, nobis, it is distinguished by having 

 narrower and more deeply concealed poriferous avenues, fewer 



