276 Dr. T. Wright on the Cidaridte of the Oolites. 



the same species^ and that the difference between them and the 

 foreign E. perlatus from the evidence afforded by the test alone 

 amounts at most to a more granular variety. We may consider 

 therefore E. perlatus, var. germinans, as characteristic of the 

 inferior stages, and E. perlatus of the upper stages of the Oolitic 

 group. E. diademata of M^Coy agrees so nearly vv^ith our speci- 

 mens of the young of this species that vs^e think them the same. 



Stratigraphical range and localities. — This Urchin is found in 

 good preservation in the inferior ferruginous beds of the Pea- 

 grit at Leckhampton, Cleeve, and Crickley Hills. Our best 

 specimens were obtained from the latter locality ; it is found in 

 the shelly freestone of the above hills, and in the Inferior Oolite 

 of Stroud, Nailsworth, Minchinhampton and Dundry ; its convex 

 prominent ambulacral columns, and the median furrow down 

 the centre of the interambulacrai arese, serving to determine the 

 species even when its other characters are effaced. On the con- 

 tinent E. perlatus is considered a characteristic Urchin of the 

 " Terrain a chailles," and was long ago described by Desmarest. 

 The specimens from the Inferior Oolite are more granular than 

 those obtained from the upper stages of the Oolitic series, but in 

 other respects the specific characters are identical. 



History. — Echinus perlatus, figured and described by Des- 

 marest and Goldfuss, has been long known to characterize the 

 upper Oolitic beds of the continent. We have no doubt that 

 Mr. Phillips^s E. germinans is at most only a variety of this 

 species found in the Inferior Oolites of England. Mr. M'Coy's 

 description of E. dimidiata corresponds so closely with young 

 specimens of this species, a series of which now lies before us, 

 that we cannot doubt their identity. 



Echinus serialis, Agass. PI. XIII. fig. 2 a, b, c, d. 

 Syn. Echinus serialis, Agassiz, Echin. Foss. de la Suisse, t. 22. 

 fig. 10^12. 



Test hemispherical, depressed^ circumference slightly pentagonal; 

 ambulacra! arese with two rows of marginal tubercles ; inter- 

 ambulacrai arese with two ranges of tubercles in the centre of 

 the columns ; base concave, mouth moderate-sized, decagonal, 

 and slightly notched ; apical disc small ; anus slightly ec- 

 centrical. 



Height 1 inch, transverse diameter 1 inch and y^^ths. 

 Description. — This Echinus resembles a Diadema in having two 

 ranges of tubercles very nearly the same size on both arese ; the 

 ambulacral are rather more than one-third the width of the inter- 

 ambulacrai arese, and are furnished with two rows of small 

 tubercles, each alternate plate supporting a tubercle on its pori- 

 ferous margin ; the interambulacrai arese are wide, and have in 



