38 SILICEOUS SPONGES. 



sition of the oscules this species also resembles V. miUaris, Reuss, but is readily 

 distinguished therefrom by the different characters of the under surface. 

 Distribution. Upper Chalk: Flamborough. 



Verruculina coxvoluta, Querist, sp. (Plate IV. figs. 1, 1 a, b, c, d.) 



1878. Spongia convohita, Qnenst. Petref. Bd. 5, p. 368, t. 132. f. 49, 50. 



1835. Spongia convoluta?, Phill. Geol. York. t. 1. f. 6. 



1870. Chenendopora tenuis, j). p., F. Koemer, Geol. Obersclil. p. 301, t. 31. f. 1. 



1878. Amphithelion convoluta, Zitt. Stud. II Ab. p. 60. 



Sponge consisting of a convoluted plate, which by the union of the lateral margins 

 frequently becomes open funnel-shaped. The wall is nearly 7 mm. in thickness, the 

 margins rounded, and sliglitly thinner than the wall. Large specimens measure 

 115 mm. in width at the summit and 100 mm. in height. 



Both the outer and inner surfaces of the sponge-wall are thickly covered witli 

 minute apertures, varying from 0-3 to 05 mm. in width. Those of the upper or 

 inner surface have very slightly elevated margins, and are somewhat further apart 

 than those of the outer surface. These latter appear generally not to possess raised 

 margins, though in some cases they are present. The canal-structures of the interior, 

 as also the spicular fibre, have been completely obliterated in all the specimens. 



In general form, thickness of the wall,. and the characters of the outer surface 

 these sponges resemble the V. convoluta, Quenst. ; but in Quenstedt's examples the 

 features of the inner surface had been obliterated, and I can only suppose that they 

 were originally similar to these forms. The figure given by Phillips of Spongia 

 convoluta, loc. cit. t. 1. f. 6, is altogether insufficient for recognition, and might be 

 applicable to two or three species of these Flamborough forms. F. Roemer has 

 figured a sponge under the name oi Chenendopora tenuis, loc. cit. t. 31. f. 1, which 

 resembles the present form very closely; and if there had been any certainty that 

 this figure really represented the original type of his brother's species, that name 

 would have had the priority. But judging from the figures and descriptions given 

 by F. A. Ecemer himself in the ' Nordd. Kreide ' and in the ' Palseontographica,' there 

 is but httle resemblance to the specimen figured by F. Eoemer in the 'Geol. 

 Oberschl.' t. 31. f. 1. The identity of Chenendopora tenuis becomes still more 

 doubtful from the fact that the second figure given of it by F. Eoemer, Geol. 

 Oberschl. t. 31. f. 3, appears to belong to a different species from the fig. 1 of the 

 same plate. 



The similarity of the apertures on both surfaces of the wall and their small dimen- 

 sions very readily distinguish this from the other species of this genus. 



Distribution. Upper Chalk : Flamborough. 



