VEREXJCULINA. 37 



walls are from 6 to 9 mm. in thickness. The margins are somewhat attenuated and 

 rounded ; and the oscules extend close to the edge of the wall. The examples are of 

 various dimensions, a large specimen measuring 170 mm. in width. 



The upper or inner wall-surface has numerous, irregularly disposed, slightly pro- 

 jecting oscules, 0-G5 mm. wide, and about 2 mm. apart ; the interspace between the 

 oscules appears to be composed of a compact membrane when perfect ; but usually 

 it exhibits closely arranged sinuous apertures. The lower or outer wall-surface is 

 roughened occasionally with shallow concentric furrows, and is traversed by thick- 

 set minute pores, 0"3 mm. each in width. In many examples the lower surface has 

 the appearance of a compact membrane ; but when treated with dilute acid the pores 

 become visible. 



Traces of the spicules can be occasionally seen ; but, as a rule, the spicular fibres 

 are destroyed, and the interior of the sponge-wall exhibits only a mass of porous 

 silica. 



From Verruculina aurita, Ecem. sp., Palseont. Bd. 13, p. 43, t. 16. f. 2, this 

 species is distinguished by the more numerous oscules on the upper surface, and the 

 very closely set pores on the lower, whilst the margins are not thickened as in 

 Roemer's species. It differs from V. seriatoporum, Rcem. sp., in the absence of a 

 linear arrangement and the smaller size of the oscules, and also by the pores of the 

 under surface. The V. PhiUipsii, Reuss, sp.. Boh. Kr. p. 77, t. 19. f. 7, has much 

 stouter walls, and there no pores on the lower surface. It seems probable that 

 Reuss has included more than one species under V. Philli])sii ; for his fig. 9 has very 

 much thinner walls than fig. 7, and the oscules are not more than half the size. 



V. flicata appears to have been abundant. 



Distribution. Upper Chalk : Flamborough ; Sudmerberg. 



Verruculina astr^a, Hinde, n. sp. (Plate III. figs. 5, 5 a.) 



Sponges fan-, cup-, or ear-shaped, with walls from 4'5 mm. to 6'5 mm. in thickness. 

 The margins rounded and of the same thickness as the wall. The specimens vary 

 from 40 to 70 mm. in lateral extension, and reach to 70 mm. in height. 



The inner surface of the wall has irregularly disposed projecting oscules, each 

 about 0-7 mm. in width. From each of these oscules sinuous canals radiate in all 

 directions. These canals extend apparently in a horizontal direction immediately 

 beneath the dermal layer. The under and outer surface of the wall has, in some 

 specimens, slight concentric ridges and furrows ; it is covered with a dermal layer 

 which is pierced by minute pore-like apertures 0"3 mm. in width, which are either 

 irregularly scattered on the surface or disposed in reticulating lines. 



This species approaches V. flicata, but is distinguished from it by tlie ladial 

 disposition of the canals round the oscules, and the irregular arrangement of the pores 

 of the under surface. The walls are also thinner. In the general form and dispo- 



