64 PEOI". p. M. DTJKCAN's EETISION 01" THE 



Peristome moderate, decagonal, and with rather deep branchial 

 incisions; ten buccal plates upon the peristomial membrane. 

 Spines long and slender, needle-shaped, longitudinally striated. 



Fossil. Lias and Oolites : England, Europe. Cretaceous : 

 Europe. 



'Recent. Caribbean Sea, 138-270 fms. ; Sigambai, Japan. 



Subgenus Echinodiadema, Cotteau, 1869 (genus), Bev. et Mag. 

 de Zool. ser. 2, vol. xxi. p. 238, pi. xli. (non VerrilT). 



Test small, subcorneal. Ambulacra with undulating or straight 

 poriferous zones ; three pairs of pores directly superimposed to a 

 compound plate, forming arcs actinally ; arrangement " diade- 

 matoid." Ambulacral and interradial tubercles nearly equal, 

 plain, most numerous and largest actinally; each interradial 

 tubercle corresponding to a swelling of a plate. Grranulation 

 distinct and distant, considerable. 



Peristome large, subcircular, with branchial incisions. 



Fossil. Oolite : Europe. 



G-enus Placodiadema, Duncan. 



Syn. Plesiodiadema, Dune, (non Pomel), 1885, Quart. Journ. 

 G-eol. Soc. Tol. xli. p. 433, fig. viii. De Loriol, 1887, Paune Cret. 

 du Portugal, Ech. fasc. i. p. 31. 



Test of moderate size, depressed, circular in marginal outline, 

 tumid dorsally and flatter actinally. 



Apical system small, compact, the five basal plates and five 

 radial plates all perforated. 



Ambulacra moderately broad, the poriferous zones with nu- 

 merous pairs of pores in simple vertical series or somewhat 

 arched ; plates high, compound, made up of from four to six 

 component primary plates, the sutures curved, with their con- 

 vexities towards the centres of the plates, the second component 

 from the adoral suture of the compound plate being the largest 

 primary component ; a pair of pores to a component plate. 

 Interporiferous areas with two vertical rows of small primary 

 tubercles, perforate and crenulate. 



Interradia wider than the ambulacra, with two or more rows 

 of primary tubercles, resembling those of the ambulacra. Peri- 

 stome decagonal, moderate, and with branchial incisions. Spines 

 striated, moderately long, hollow (see specimen in Brit. Mus.). 



Fossil. Oolite : Europe. Cretaceous : England and Europe. 



