FROM THE CORAL RAG. 215 



Ranville, Calvados, by M. Tesson, in which the apical disc is preserved. It is small and 

 prominent; the genital plates are nearly equal-sized, the right anterior plate is the 

 largest, and the spongy madreporiform body occupies all the surface of that plate ; the 

 oculars are small, and deeply indented where they receive the apex of the ambulacra ; the 

 genital holes are perforated about the outer third of the plates ; the vent is oblong, and its 

 long diameter lies obliquely across the test. It is doubtless a rare urchin in France, as 

 none of the systematic authors make mention of it ; or it may be that it has hitherto been 

 confounded with Polgcgphus Normannus. 



C. Species from the Coral Bag — 14 e Etage Corallien, d'Orbigny. 



Stomechinus gyratus, Agassis. PI. XIV, fig. 4 a, b, c, d, e. 



Echinus gyratus. Agassiz, Echinoderm. Fossiles de la Suisse, part ii, p. 87, pi. 23, 



figs. 34—46. 



— petallatus. M'Coy, Annals and Magazine of Natural History, 2d series, 



vol. ii, p. 409. 



— gyratus. Agassiz and Desor, Catalogue raisonne" des Echiuides, Annales des 



Sciences Naturelles, 3 me serie, torn, vi, p. 366. 



— gyratus. Wright, Annals and Magazine of Natural History, 2d series' 



vol. ix, p. 85. 



— — Forbes in Morris's Catalogue of British Fossils, 2d edit., p. 79. 



— — Salter, Memoirs of the Geological Survey, Decade V. Notes on 



Echinus, p. 8. 

 Stomechinus gyratus. Desor, Synopsis des Echinides Fossiles, p. 126. 



Test hemispherical, more or less elevated, inflated at the sides, round at the 

 circumference ; sides divided by depressions into fifteen unequal, slightly convex lobes ; 

 ambulacral areas half the width of the inter-ambulacra], with two complete rows of 

 marginal tubercles extending from the peristome to the disc, and two incomplete rows of 

 central tubercles occupying two thirds of the sides ; inter-ambulacral areas divided into 

 lobes by naked median depressions, which extend from the disc to the circumference . 

 each lobe has one complete central row, and four incomplete lateral rows of secondary 

 tubercles ; apical disc central ; vent small ; mouth opening wide ; peristome pentagonal. 



Dimensions. — Height, one inch ; transverse diameter one inch and four tenths. 



Description. — This beautiful urchin was figured, with details, by M. Agassiz, in his 

 ' Echinodermes Fossiles de la Suisse ;' its specific characters are so well marked that it can 

 scarcely be mistaken for any other species. The test is hemispherical, more or less 



