PODOCIDARIS SCULPTA. 269 



unless the spines cited under the name of Cidaris incerta D'Arcii., in Mem. 

 Soc. Geol. Vol. III. 2d Ser. Mem. 6, p. 420, PI X. f. 11, found in the same 

 beds as those containing Coelopleurus, should turn out to be the spines of 

 this genus. They greatly resemble the smaller, shorter, and straight spines 

 of Keraiaphorus found round the actinostome, as was suggested to me by 

 Mr. Vaillant of the Ecole des Mines. 



Nor is there any mention made of the sutural impressions found between 

 actinostome and ambitus in the median ambulacral space. These impres- 

 sions were first noticed by Cotteau * in a fossil species ( C. Delbosii) from 

 the lower tertiaries of Gironde ; although Michelin has not described them, the 

 accurate pencil of Humbert has not failed to show them in the figure of the 

 test, as seen from the actinal side (in PI, XIV. f. 2, of Michelin's paper). 



It is interesting to note in this connection the existence of a fossil species 

 of this genus from the London Clay, described by Forbes in his Brit. Tertiar. 

 Echinoderms, under the name of Coelopleurus Wetherelli; we have also in the 

 Tertiaries of Alabama and of Bordeaux species of Coelopleurus. 



PODOCIDARIS. 



Podocidaris A. Aoass. 1869. Bull. M. C. Z., I. 



Test regularly arched above, flat below, depressed abactinal surface, sur- 

 rounded by raised ambulacral ridges ; actinal system resembling that of 

 Arbacia ; primary tubercles carrying large, spindle-shaped spines, confined to 

 lower surface. Actinal membrane imbricated only towards centre from the 

 buccal plates. Abactinal part of test covered by spines not articulated, 

 rising directly from test ; median ambulacral and interambulacral spaces 

 deeply pitted by depressions surrounded by the ridges extending from the 

 base of the rudimentary club-shaped spines. Poriferous zone narrow ; a 

 single vertical row of pairs of pores ; abactinal system large, resembling 

 that of Arbacia ; anal system covered by four large plates. 



Podocidaris sculpta 



! Podocidaris sculpta A. Ag. 1869. Bull. M. C. Z. 



PI. IV. f. 8-16. 



This species has, at first glance (PI. IV. f. 8), the general facies of a young 

 Arbacia, with a depressed abactinal surface, the ambulacra rising in ridges 



* Echinides Nouveaux, Rev. Mag. Zool., August, 1864, p. 105, PI. XIV. f. 10. 



