ELASMOSTOMA. 195 



Owing to the meagre and unsatisfactory definition of this species by Michelin, very 

 various forms have been assigned to it by different authors, and it is difficult to deter- 

 mine which of these should properly be included in it. I have applied it to sponges 

 resembling the forms figured by Geinitz, though I do not agree with this author in 

 including therein the Manon Pezha figured by Goldfuss in Petref. 1 Th. t. 29. f. 8, 

 which appears to me to belong to a different species. 



Distribution. Upper Green Sand : Warminster. Cenomanian : Essen. 



Elasmostoma consobrinum, BOrhigny, sp. 



1847. Cupulospongia consobrina, D'Orbigny, Prodr. de Pal. vol. ii. p. 188. 



1826-33. Manon peziza, Goldf. pars, Petref. 1 Th. t. 1. f. 7, 8. 



1871. Elasmostoma consobrinum, Geinitz, Pal. Bd. 20, p. 38, t. 6. f. 8-10. 



1878. Manon peziza, Quenst. pars, Petref. Bd. 5, p. 358, t. 132, f. 26-33. 



1878. Elasmostoma consobrinum, Zitt. Studien, III Ab. p. 45. 



1883. Elasmostoma consobrinum. Dun. Pal. Bd. 29, p. 41, t. 37. f. 4, 5. 



Cup- or fan-shaped sponges with walls from 2 to 4 mm. in thickness. One surface 

 of the wall, usually the outer or convex surface, is penetrated by minute circular 

 apertures about -5 mm. in width ; the opposite surface has no special dermal layer, 

 and merely shows the interspaces between the fibres. The fibre, according to 

 Dunikowski, is composed mainly of relatively large axial three-rayed spicules. 

 D'Orbigny's definition of this species is obviously insufficient for recognition, but 

 as the name has been applied by later authors to the sponges figured by Goldf. in 

 Petref. pi. 1, f. 7, 8, I have used it for these forms. As pointed out by Geinitz, the 

 sponges figured by Goldfuss were derived from Essen, and not, as erroneously stated, 

 from Maestricht. 



IMstrihution. Upper Green Sand : Warminster. Cenomanian : Essen. CIraie 

 Chloritee : Villers-sur-Mer. 



Elasmostoma scitulum, Hinde, n. sp. (Plate XXXVI. figs. 6, 6 a, 6 i, 6 c, G d.) 

 Sponges growing in flattened or slightly convolute fan- or plate-shaped expansions 

 from 40 to 100 mm. in height, and from 50 to 110 mm. in width. The base is 

 either expanded or variously curved. The wall is from 4 to 5 mm. in thickness. 

 The inner or concave surface of the wall has a smooth dermal layer, perforated by 

 circular apertures about 1-5 ram. in width, and from 1-5 to 3 mm. apart. The 

 margins of these apertures are thickened and, wheve best preserved, slightly elevated 

 above the surface. The surface between the larger apertures is also perforated by 

 minute irregular puncta. The under surface of the wall is rough ; the fibres have 

 an indistinct radiate arrangement, and are connected by minute angular processes. 

 In a transverse section the fibres measure from -1 to -35 mm. in thickness. The 



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