U2 SILICEOUS SPONGES. 



walls of the interior are about 1 mm. in thickness ; the octahedral nodes of the mesh 

 are "38 mm. apart. 



The larger size and the dome-shaped summit distinguish this species from C. capi- 

 fata ; the spicular mesh is also smaller. The figures H and I of T. Smith (loc. cit. 

 p. 291), representing the disposition of the folds of the wall, are purely diagrammatic. 

 In the typical examples the wall-plaits do not exhibit the regularly arranged folds 

 depicted in these figures. 



Distribution. Upper Chalk : South of England [coll. T. Smith). 



Cameeospongia apeeta, Einde, n. sp. (Plate XXX. figs. 2, 2 a, 2 b.) 

 1848. Cephalites campanulatus, T. Smith, pars, Ann. & Mag. Nat. Hist. vol. i. t. 14. £. 3. 



Sponges depressed, cup-shaped, supported on a short stem with diverging rootlets. 

 The interior exhibits a funnel-shaped cloacal cavity, bounded by a definite wall ; the 

 margins are subacute. The lateral surfaces are smooth and slightly uneven ; the 

 under surface is formed by uneven ridges with irregular interspaces. A few irregu- 

 larly convoluted wall-plaits are shown in a vertical section ; the spicular mesh has a 

 regular disposition; the octahedral nodes are "25 mm. apart. The spicular mesh of 

 the walls of the cloaca is of the same character as that forming the interior plaits. 

 The body of the type specimen is 25 mm. in height by 36 in width. 



This species difi"ers from C. campanulata, as defined above, by its generally smaller 

 size, the widely expanded cloacal aperture, the definite cloacal wall, and the smaller 

 dimensions of the spicular mesh. 



Distribution. Upper Chalk : South of England [coll. T. Smith). 



Genus CYSTISPONGIA, F. A. Bcemer, 1864. 

 Ctstispongia btjesa, Quenst. sp. 



1852. Cephalites bursa, Quenst. Handbuch d. Petref. p. 670, t. 60. f. 17. 



1864. Cystispongia bursa, F. A. Roemer, Palaeontographica, vol. xiii. p. 7, t. 4. f. 7. 



1877. Cysiisponffia bursa, Zitt. Studien, I Ab. p. 57; Neues Jahrbuch, p. 368; Handb. d. 

 Pal. p. 182, f. 98. 



1878. Cephalites bursa, Quenst. Petref. Bd. 5, p. 492, 1. 138. f. 17. 



Distribution. Obere Planer : near Vienenburg, Prussia {coll. Zitt.). 



Family CALLODICTYONIDM, Zittel. 



Genus CALLODICTYON, Zittel, 1877. 



Callodictyon angustatum, Einde, n. sp. (Plate XXX. figs. 4, 4 a, 4 b.) 

 Sponges elongate, funnel-shaped, very gradually tapering from the summit to the 



