144 SILICEOUS SPONGES. 



1851. Spongia Townsendi, Morris, Catalogue, p. 31. 



1878. Ventriculites simplex, Quenst. Petref. Bd. 5, p. 470, t. 137. f. 17. 



Sponges funnel-shaped, either supported on a cylindrical stem with divergent 

 rootlets or having rootlets springing from the base of the funnel. Variable in size — 

 from small forms, 22 mm. in height by 30 in width at the summit, to large examples, 

 95 mm. in height and 92 in width. 



The walls are frequently very compressed ; in the best-preserved specimens they 

 are from I'S to 2 ram. in thickness. The exterior layer is smooth, and sometimes 

 exhibits concentric markings. The dermal layer is perforated with irregularly 

 disposed circular or oval apertures, about '5 mm. in width, and the same distance 

 apart. The spicular mesh is regularly subquadrate ; the octahedral nodes are '43 mm. 

 apart. The spicular structure of the stem and rootlets differs from that of the walls, 

 and consists of a network of elongate spicular fibres. 



The examples of this species are abundant ; in all cases the spicular structure is 

 either in the condition of iron peroxide or in hollow casts. 



According to T. Smith, Sjwngus Toionsendi, Mant.*, is nothing more than a 

 V. simplex in flint. If such were certainly the case the specific name of Mantell 

 ought to have been retained ; but the type of Mantell, now in the Museum, is so 

 completely imbedded in flint that its spicular characters cannot be ascertained, and 

 it might belong to an entirely different form from Smith's species. 



The sponge figured by the late Sir Wyville Thomson, in the ' Depths of the Sea'f, 

 •iS Ventriculites simplex, T. Smith, and from thence copied into other works, has no 

 resemblance to Smith's species, though it may possibly be a genuine specimen of 

 Ventriculites. 



Bistributioti. Upper Chalk : Lewes, Sussex ; Charing, Kent (coll. Mantell and 

 C. Smith). 



Genus BECKSIA, Schliiter, 1868. 

 Becksia Scekelandi, Schliiter. 



1868. Becksia Sakelandi, Sclil. Sitzuiigsb. der nieder. Gesells. im Bonn, p. 93. 

 1872. Becksia Scekelandi, Schl. Ueber die Spongit.-Baenke des Miinsterlandes, p. 20, t. 1. 

 f. 5-7. 



1877. Becksia Scekelandi, Zilt. Studien, I Ab. p. 58; Neues Jahrbuch, p. 369. 



1878. Becksia Swkelandi, Quenst. Petref. Bd. 5, p. 489, t. 138. f. 14. 

 1878. Becksia Swkelandi, Zitt. Handb. der Pal. 1 Tb. p. 183, f. 99. 



Distribution. Upper Chalk : Coesfeld, Westphalia. 

 • Fossils of the South Downs, p. 154, t. 15. f. 19. f P. 483, f. 80 ; p. 484, f. 81. 



