40 SILICEOUS SPONGES. 



The Flamborough examples have the oscules of the upper surface more projecting 

 and less numerous than in Reuss's figure 11 «, which I take as the typical form of 

 the species ; as, however, the similarity in other respects is very close, I did not 

 regard the difference in this feature as of sufficient importance to place them as a new 

 species. Reuss states in his description of this species that the openings of the outer 

 surface are larger and more projecting than those of the inner surface ; but a glance 

 at his figures plainly shows that the surface which he terms " outer" is in reality, in 

 the case of the funnel-shaped specimens, the inner surface. From the V. aurita, 

 F. A. Roemer *, this form is distinguished by the projecting apertures of the under 

 surface. 



Distribution. Upper Chalk : Flamborough. 



Verruculina Reussii, M'Coy, sp. (Plate V. figs. 1, la.) 



1848. Manon Reussii, M'Coy, Anu. & Mag. Nat. Hist. vol. ii. p. 398. 

 1878. Manon circumporosum, Qiienst. Petref. Bd. 5, p. 372, t. 132. f. 55. 



Sponge forming large horizontal plate-like expansions, or in the form of a shallow 

 dish or cup, growing from a short peduncle. The margins are rounded, either even, 

 lobed, or occasionally digitate. The thickness of the wall is from 10 to 12 mm. A 

 large example measures 190 mm. in width. 



Both surfaces of the sponge-wall possess a thickened dermal layer. The oscules 

 are carried on the summits of small papillae; they are 1-75 mm. in width each, and 

 are disposed irregularly on both surfaces, from one to three diameters apart. The 

 oscules of the under surface are somewhat less projecting than those of the upper, 

 but they are nearly equal as regards size. 



The interior of the wall is composed of a labyrinthine web of very delicate 

 anastomosing fibres ; there are no indications of distinct canals. The spicules 

 composing the fibre cannot be distinguished. 



The thickness of the walls and the large size of the oscules on both surfaces 

 readily characterize this species. No figure accompanied M'Coy's description ; but 

 there is no difficulty in recognizing the species from his description. The example 

 figured by Quenstedt under the name of Manon circumporosum appears to belong to 

 this species. 



The examples are numerous and w^ell preserved. 



Distribution. Upper Chalk : Flamborough. 



Verruculina macrommata, Eoein. sp. 



1864. Verrucospongia macrommata, Rcemer, Palieon. Bd. 13, p. 45, t. 16. f. 4. 

 1878. Amphithelion macrommata, Zitt. Stud. II Ab. p. 60, t. 3. f. 15. 



Microscopic slide with detached spicules of this species. 

 Distributioi) . Upper Chalk: Ahlten, Hanover. 



* Palffiontographica, Bd. 13, p. 43, t. 16. f. 2. 



