GENERA AND GROUPS OP THE ECUINOIDEA. 73 



Apical system large, grauukr, flush ; basals large, high, ex- 

 tending into the interradia somewhat ; radials small ; periproct 

 small, pentagonal. 



Ambulacra narrow, straight, having distant, large, perforate, 

 non-crenulate primary tubercles on the flat actinal surface and 

 near the ambit'as only. Pairs of pores iu oblique triplets, the 

 aboral pair being nearest the interradium, and the adoral nearest 

 the median ambulacral line. Plates low, compound, the three 

 components being " diadematoid" primaries. 



Interradia -with large perforate non-crenulate tubercles dimin- 

 ishing abaetiually ; plates high and granular. 



Peristome large, decagonal ; branchial incisions large. 



Fossil. Oolite : Europe. 



The size of the primary tubercles characterizes this subgenus 

 of Pedina. 



Grenus Echhstopedina, Cotteau, 1866, Rev. et Mag. de Zool. 

 ser. 2, vol. xviii. p. 362. 



Syn. EcJiinopsis (pars). 



Test moderate, spheroidal or subspheroidal, flattened above 

 and actinally. 



Apical system with a narrow ring and a large madreporite ; the 

 posterior radials entering the periproctal ring. 



Ambulacra broad and straight, with broad poriferous zones, 

 the pairs in decided arcs of triplets, more or less biserial or tri- 

 serial ; a vertical row of perforated, non-crenulate small primary 

 tubercles close to each poriferous zone ; small secondaries or 

 large granules nearer the median line. 



Interradia with tvvo vertical rows of small primary tubercles 

 resembling those of the interradia, the broad median space being 

 occupied by rows of granules or small secondaries. 



Peristome small, and with branchial incisions fairly developed. 



Fossil. Eocene : England and Europe ; America, Cuba. 



The arched nature of the triplets of the ambulacra distinguishes 

 Mchinopedina from Echinopsis. JEcliinopedina Gaclieti of the 

 Erench Eocene is the type. 



Cotteau has described Ecliinopedina cnhensis from the Eocene 

 of Cuba (Ann. de la Soc. Geol. de Belg. t. ix. Memoires, 1881, p. 9, 

 pi. i. figs. 1-6) ; and it only departs from the generic character 

 by having a second vertical row of small primary and some 

 secondary tubercles. The figure 3 of Cotteau's plate i. shows 



