210 STOMECHINUS. 



beautiful specimen in the Trigonia grit of Hampen, Gloucestershire, with Pedina rotata, 

 Holcctypus depressus, and Collyrites hemispharicus. The Rev. A. W. Griesbach collected 

 one specimen in the Cornbrash, at Rushden, Northamptonshire ; and Mr. Buy obtained 

 another from the Cornbrash, near Sutton, Wilts. 



Stomechinus bigranularis, Lamarck. PI. XIV, fig. 3 a, b, c, d, e. 



Echinus bigranularis. Lamarck, Animaux sans Vertebres, tome iii, p. 50. 



— — Agassiz and Desor, Catalogue raisonne des Echinides, Annal. 



des Sciences Naturelles, 3 me serie, tome vi, p. 365. 



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



vol. viii, p. 276", pi. 13, fig. 2. 



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



— perlatus, var. Forbesii. Salter, Memoirs of the Geological Survey, Decade V, 



pi. 4, fig. 6. 

 Stomechinus bigranularis. Desor, Synopsis des Echinides Fossiles, p. 125, tab. xviii, 



fig. 5—7. 



Test hemispherical, depressed ; sides inflated, circumference more or less sub-penta- 

 gonal ; ambulacral areas with two rows of small tubercles on the margins, placed wide 

 apart, twenty-six in each row, and a very fine granulation between ; poriferous zones 

 narrow, trigeminal ranks not very oblique, becoming nearly parallel on the upper and 

 under surfaces ; inter-ambulacral areas with two rows of primary tubercles, twenty in each 

 row, and two short rows of secondaries, which disappear at the circumference; miliary 

 zone wide, and uniformly covered with small, equal-sized granules ; mouth opening small ; 

 peristome pentagonal, with ten shallow, obtuse notches ; apical disc large, excentral ; all 

 the genital plates, with the exception of the right antero-lateral, small ; vent large, and 

 encircled by a moniliform line of small granules. 



Dimensions. — Specimen a, fig. 3 a. Height, one inch and one fifth ; transverse 



diameter, one inch and seven tenths. 

 „ b, fig. 3 b. Height, one inch and seven twentieths ; trans- 

 verse diameter, two inches. 



Description. — This species is supposed to be Echinus antiquus, Defrance MSS., and 

 Echinus bigranularis, Lamarck, although this is not quite clear. M. Desor says — 

 • : I have been for a long time in doubt as to the identity of this species, which was so 

 much more difficult to define, as, among the originals in the Paris Museum, ticketed by the 

 hand of Lamarck, there are found many species. After much hesitation, I propose to 



