196 CALCAEEOUS SPONGES. 



spicular structure is distinctly of the Sestrostomella type ; a single ray of one of the 

 large axial spicules measures '24 mm. 



In its general characters Manoii Peziza, Goldf. Petref. 1 Th. t. 29. f. 8, resembles 

 this species ; but the oscular apertures are uniformly single, and they are closer 

 arranged than in Goldf uss's form. 



Distribution. Upper Chalk : Charlton, Bromley, Kent ; Sussex. 



Elasmostoma crassum, Hinde, n. sp. (Plate XXXVI. fig. 7.) 



Sponges growing in irregularly folded expansions ; the only specimen is imperfect, 

 and measures 76 mm. in width and the same in height. The walls are from 6'5 to 

 10mm. in thickness; the inner or upper surface is smooth, and is perforated by 

 circular apertures from 1-6 to 2 mm. in width, and about the same distance apart ; 

 their margins are smooth and even. Between the larger apertures are smaller 

 irregular perforations. The under surface resembles that of the last species. 



The fibres are from '13 to "4 mm. in thickness ; in the specimen examined they are 

 entirely crystalline, and no structure has been preserved. 



This species may be readily distinguished from the preceding by the much greater 

 thickness of the walls and the larger size of the oscular apertures. 



Distribution. Upper Chalk : Bromley, Kent. 



Elasmostoma plicatum, Hinde, n. sp. (Plate XXXVII. fig. 1.) 



Sponges with convolute walls, either fan- or open funnel-shaped. A fairly large 

 specimen is 95 mm. in width and 57 mm. in height. The walls are 4 mm. in thick- 

 ness. The inner surface has circular apertures 1 mm. wide, and from 1 to 2 mm. 

 apart, with minutely punctate interspaces. The under surface of the wall resembles 

 that of E. scitulum, but the fibres are of a more delicate character. 



In a thin transverse section the fibres measure about •17 mm. in width; their 

 spicular structure resembles that of E. scitulum, and they are generally narrower, 

 and more evenly disposed than in that species. 



This species approaches closely to E. scitulum ; but the oscular apertures are 

 smaller, and the fibres are less robust. 



Distribution. Craie Chloritee : Cap la Heve, near Havre. 



Elasmostoma subpeziza, DOrb. sp. 



1847. Cupulospongia subpeziza, D'Orb. Prodr. de Pal. vol. ii. p. 288. 

 1826-33. Manon peziza, Goldf. pars, Petref. 1 Th. t. 5. f. 1. 

 1878. Manon peziza, Quenst. pars, Petref. Bd. 5, p. 363, t. 132. f. 42, 43. 

 1878. Pharetrospongia subpeziza, Zitt. Studien, III Ab. p. 46. 



Sponges small, obliquely cup-shaped ; a fairly large example is 19 mm. in height 

 by 17 in wndth. The walls are from 2 to 2-5 mm. in thickness. The outer surface 



