204 STOMECHINUS. 



A. Species from the Inferior Oolite. 



Stomechinus germinans, Phillips. PL XIV, fig. 1, a, b, c, d. 



Echinus germinans. Phillips, Geology of Yorkshire, pi. 3, fig. 15, p. 127. 



— — ■ Murchison, Geology of Cheltenham, 2d edit., p. 73. 



— — Morris, Catalogue of British Fossils, p. 52. 



— perlatus, var. GERMINANS. Wright, Annals and Magazine of Natural History, 



2d series, vol. viii, pi. 13, fig. 1 a — d, p. 274. 



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



vol. ii, p. 410. 



— perlatus. Forbes, in Morris's Catalogue of Brit. Foss., 2d edit., p. 79. 



— — Salter, Memoirs of the Geological Survey, Decade V, pi. 4. 

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



— sub-conoideus. Desor, Synopsis des Echinides Fossiles, p. 125. 



Test high, conoidal ; marginal fold acute, circumference sub-pentagonal ; ambulacral 

 areas with two rows of primary tubercles, thirty-four in each row ; poriferous zones wide, 

 the trigeminal ranks lie very obliquely across the zone ; inter-ambulacral areas with one 

 central row of primary tubercles in the middle, two rows of secondaries on the zonal, and 

 one on the centro-sutural side of each column of plates ; miliary zone wide and finely 

 granulated, with a naked median depression in the upper half; apical disc small, excentral ; 

 genital plates very narrow, vent transversely oblong, base concave ; mouth opening very 

 large ; peristome pentagonal, with bifid-notched angles, the ten notches wide and deep. 



Dimensions. — Height, one inch and a half; transverse diameter, two inches. 



Description . — Since the publication of my ' Memoir on the Cidaridse of the Oolites,' 

 in which this urchin was first described, I have obtained specimens of Echinus perlatus, 

 Desmarest, which has enabled me to make a critical comparison between our specimens 

 and the species to which it was referred, and I have thereby been enabled to correct errors 

 in my previous determination. 



The test of Stomechinus germinans, especially in adult specimens, is always high and 

 conoidal (fig. 1 a) ; the sides rise abruptly from an acute marginal angle ; the prominence 

 of the ambulacra, and the median depression in the inter-ambulacra, impart a lobed 

 appearance to its upper surface. 



The ambulacral areas are one third the width of the inter-ambulacral (fig. 1 a, c) ; 

 they are very uniform in breadth throughout, and from being convex and prominent, 

 give a sub-pentagonal form to the circumference ; they have two rows of tubercles on 

 their margins, from thirty to thirty-four in each row, a smaller tubercle often alternating 



