444 Scientific Proceedings, Royal Dublin Society. 



Skeleton. Small, slender rliizomorine corpuscles, arranged upon 

 no evident plan. 



Horizon. Marlstone, Lias, 



Locality. Ilminster, Somerset. 



Remarks. The form of the sponge is such as would be produced 

 by the incurving growth of a lobate fan-shaped expansion to form 

 an irregular cup. The highest part of the cup represents the 

 median line of the fan, the lowest part the united edges. An 

 incrustation of oolitic rock covers the surface in places ; but, when 

 this is absent, a dark-brown ferruginous layer is evident, in which, 

 however, no structure such as might indicate the presence of a 

 special dermal covering layer is discernible. On treating the 

 surface with acid the ostia are rendered visible, as round or oval 

 areas, bounded by the skeletal corpuscles in characteristic Lithis- 

 tid fashion. They are not quite so well defined on the inner 

 surface of the wall, and, though oval and round in most cases, 

 appear there sometimes as quite irregular spaces. 



The originally siliceous skeleton has been entirely replaced by 

 carbonate of lime, and the structure of the nodes of the skeleton 

 where interlocking occurred is completely obliterated. The cor- 

 puscles do not offer any characters which can be made use of for 

 the discrimination of the species. Several sections of Milliola occur 

 in the adherent rock-material. 



Cratictjlae-ia calathus* (sp. n.). 



Sponge, vasiform or funnel-shaped, with undulating margin, 

 slightly expanded above ; tapering below to form a short stem, 

 which ends abruptly in an oval scar ; no evidence of attachment ; 

 height, 51 mm. ; maximum diameter, 60 mm. ; minimum, 36 

 mm. Wall of nearly uniform thickness, 6 to 7 mm., rounded 

 at the edge, on the outside without ostia, on the inside bearing 

 ostia arranged in vertical and horizontal rows more or less at right 

 angles to each other. 



Ostia apparently oval, elongated longitudinally ; in a horizontal 

 row 6 occur in a distance of 9 mm. ; in a vertical row 5 in 12 mm. 



Skeleton. Nodes not thickened, and imperforate. 



* KaKaOos, 6, a basket. 



