188 PEOF. p. M. Duncan's EETisioisr or the 



rudimentary phyllode. Pairs of pores in the petaloid parts, witli 

 the inner pore small and circular, the outer elongate transversely 

 and in a decided long groove ; pairs close, in simple low broad 

 plates, and the costge granular. 



Interradia with broad, bent, low plates, much higher than 

 any of the ambulacral plates, with a very delicate small tuber- 

 culation, largest actinally ; tubercles scrobiculate, with a low 

 broad boss and small sim.ple mamelon ; intermediate granulation 

 rough. 



Peristome subcentral or excentric in front, pentagonal, with 

 narrow tumid granular or minutely tuberculated bourrelets and 

 narrow phyllodes in grooves. Periproct in a groove along the 

 median line of the posterior interradium, supramarginal, high up ; 

 the length of the groove variable, or the opening may be almost 

 flush with the rest of the test. 



Fossil. Oolite : England, Europe. 



Subgenus Cltpeopygtjs, d'Orligny (genus), 1856, Pal. Fran^., 

 EcMn. Terr. Gr'et. vol. vi. p. 418. Besor, 1858, Synopsis, 

 p. 273 (genus). 

 Clypei with the apical system excentric in front, and narrow 

 poriferous zones. 



Fossil. Oolite : England, Europe. Cretaceous : Europe. 



Genus Ptgtjetjs, Agassiz, 18.39, Ech. Foss. de la Suisse, p. 68 ; 



1847, Cat. Bais. des Ech., Ann. d. Sci. Nat. vol. vii. p. 161. 



Gotteau of Triger, 1859, Ech. de la Sartlie, p. 65, pi. xiii. 



Desor, 1858, Synopsis, p. 309. De Loriol, 1888, Mem. Soc. 



d. Phys. et PList. Nat. Geneve, vol. xxx. no. 2, p. 102. 

 Test large, discoid, angular or undulating in marginal contour 

 or not, and may be emarginate ; depressed, subcorneal, or rather 

 tall and conical dorsally, enlarged and rostrated behind; ambulacra 

 grooved actinally, and tbe surface otherwise flat or tumid there. 

 Apical system central or excentric in front, small, with four or 

 five basal plates, disunited, four with ducts ; madreporite extending 

 from the right anterior to the centre of the system ; radial plates 

 five, small, between the basals, and reaching the madreporite. 



Ambulacra flush dorsally, unequal, long, the lanceolate, open 

 petaloid parts reaching far to the ambitus, and tend to, but do 

 not close, continued as narrow lines of pairs of small pores over 



