66 PBOF. p. M. DUNCAISr's REVISION OF THE 



Genus Pleueodtadema, Be Loriol, 1870, Ech. Selv. Jura, p. 196 ; 

 and 1885, Mem. Soc. Pal. Suisse, Geneve, p. 18. 



Test of moderate size, more or less swollen above and flat below. 



Apical system well developed, flush, compact. 



Ambulacra narrow at the apex, with some projecting, imper- 

 forate, smooth or slightly crenulate tubercles on the actinal sur- 

 face only, the rest granular. Poriferous zones straight; pairs of 

 pores in simple series, directly superimposed and separated by 

 small horizontal costse, which are raised, distinct and stout, 

 especially actinally, and are prolonged to the interradial tu- 

 bercles. 



Interradia actinally and at the ambitus with two rows of wide- 

 apart, projecting tubercles with large mamelons, without scrobi- 

 cules, and imperforate, slightly crenulate. Very small tubercles 

 abactinally, secondary tubercles absent. 



Peristome decagonal, with everted edges ; branchial cuts small. 



Fossil. Jurassic : Europe. 



Grenus Magkosia, Michelin, 1853, Bev. et Mag. de Zool. ser. 2, 

 vol. V. p. 34. Desor, 1858, Synopsis, p. 115. Be Loriol, 

 1887, Faune Cret. du Portug., Ech. fasc. i. p. 59. 



Test small or moderate, circular at the tumid ambital outline, 

 subhemispherical dorsally, or depressed, concave actinally. Co- 

 ronal plates numerous, low. 



Apical system small ; periprocfc small. 



Ambulacra narrow except actinally, where they are broad ; 

 pairs of pores in simple straight series, barely in slight arcs of 

 triplets, but near the peristome they become close and polyserial. 

 Plates compound. Interporiferous areas with from two to six 

 or more oblique rows of very small plain primary tubercles. 



Interradia with a median depression, abactinally, which is 

 smooth ; from four to nine horizontal or oblique rows of very 

 small tubercles resembling those of the ambulacra, diminishing 

 in number abactinally. 



Peristome very large, pentagonal, well incised, the ambulacra! 

 lips the largest. 



Fossil. Oolite : England and Europe. Cretaceous : Europe 

 and N. Africa. 



The Liassic species described by M. Cotteau cannot well enter, 

 and, as he suggests, should be removed. 



