42 SILICEOUS SPONGES. 



There is a great variety in the size, from small specimens measuring 130 mm. in 

 height by 37 mm. in greatest width to large individuals 390 mm. in length by 

 120 mm. in width. 



The openings of the vertical canals usually project slightly above the summit of 

 the sponge ; they vary between 3 and 7 mm. in diameter in different specimens. 

 There is an example of this species, now in the Jermyn-Street Museum, which has 

 the vertical canals partially separated from each other so as to form a group of 

 chimney-like elevations near the summit of the sponge. The lateral surfaces are 

 covered with numerous circular apertures, with slightly projecting thickened margins. 

 In weathered specimens the margins are usually smooth. These apertures are some- 

 times in close contact ; sometimes they are disposed in sinuous lines, which apparently 

 indicate the presence of canals immediately beneath the dermal layer. 



The internal skeleton appears to be composed of anastomosing fibres ; the spicular 

 structure has been destroyed. 



This species may be readily distinguished by its large size, mode of growth, and 

 the dimensions of the vertical and lateral apertures. It appears to be a very common 

 form at Flamborough ; and there is a single specimen — now composed of iron 

 peroxide — from the Chalk of the south of England. 



Distribution. Upper Chalk: Flamborough, Yorkshire ; Bromley, Kent. 



Genus JEREICA, Zittel, 1878. 



Jereica punctata, Iliinst. sp. 



1833. Siphonia punctata, Muust., Goldf. Petref. Ger. Tli. 1, p. 221, t. 65. f. 13. 

 1878. Spumispongia punctata, p. p., Quenst. Petref. Bd. 5, p. 402, t. 13-t. f. 12. 

 1878. Jereica punctata, Zittel, Stud. II Ab. p. 63, t. 5. f. 1. 



Distribution. Upper Chalk: Sudmerberg, Goslar. 



Jereica poltstoma, Eoemer, sp. 



1864. Jerea polystoma, F. A. Rcemer, Palseon. Bd. 13, p. 34, t. 12. f. 5. 

 1878. Jereica puly stoma, Zitt. Stud. II Ab. p. 63, t. 4. f. 11, 12. 



Microscopic spicules of this species from Zittel's collection. 

 Distribution. Upper Chalk : Ahlten, Hanover. 



Jereica clava, Lee, sp. 



1839. Siphonia clava, Lee, Magazine of Nat. Hist. vol. iii. p. 12, f. 2, 3, 4. 



1840. Siphonia ocellata, F. A. Roemer, Nordd. Kr. p. 5, t. 2. f. 2. 



Sponge simple, straight, elongate, club-shaped, with a conical summit. Greatest 

 W'idth a short distance below the summit ; from thence it gradually tapers to the 



