82 SILICEOUS SPONGES. 



in the one figured ; but whether these were originally filled with sponges with yet 

 slenderer stems than the present form I am unable to determine, for no fragments of 

 the sponges remain. 



Distribution. Upper Chalk : South of England. 



Genus RAGADINIA, Zittel, 1878. 



The typical and, up to the present, only described species of this genus, Bagadinia 

 rimosa, Roemer *, sp., consists of ear- or platter-shaped sponges, with a short lateral 

 stem and thick walls. There are in the Museum collection several species of sponges 

 which correspond with the typical form of Zittel in the interior spicular structure, 

 and also in the spicular structure of the dermal layer and in the characters of the 

 canals, but differ in their exterior form. These sponges are either cup- or vase- 

 shaped, or irregularly club-shaped. As these sponges are similar in the important 

 features of their spicular and canal-structures, I propose to extend Zittel's definition 

 of the genus so as to include sponges of the above-mentioned forms. 



Ragadinia rimosa, Roemer, sp. 



1864. Cupulospongia rimosa, F. A. Roemer, Palseont. Bd. 13, p. 51, t. 17. f. 8. 



1878. Ragadinia rimosa, Zittel, Studien, II Ab. p. 88, f . 4 a-f; and Handbuch, p. 166, f. 79. 



Microscopic slides of the interior spicules and of the spicules of the dermal layer, 

 from Professor Zittel. 



Distribution. Upper Chalk : Ahlten, Hanover. 



Ragadinia compressa, Hinde, n. sp. (Plate XIX. figs. 3, 3 a.) 



Sponges vase- or funnel-shaped, frequently compressed, though some examples 

 are open and shallow, supported on a short stout stem, which is attached to some 

 foreign object at its termination. Not infrequently there are nodose outgrowths in 

 the lower part of the cup. Walls comparatively thick, varying Ixom 10 to 13 mm. 

 The margins are rounded, and occasionally show fine, transverse, open canals. The 

 specimens are from 80 to 113 mm. in height, and about the same in breadth at the 

 summit of the cup. 



The upper or interior surface of the cup is furrowed irregularly by minute open 

 canals ; the under surface exhibits also a series of delicate canals with a downward 

 direction. These canals are only apparent in some specimens : usually the outer 

 surface has numerous apertures of canals, 1 mm. in width, which open very obliquely 

 to the surface. 



The spicules of the interior mesh are minute and very characteristic in form. One 

 of the four arms merely consists of a prominent tubercle ; the other three arms have 



* Palaeontograpliica, Bd. 13, p. 51, 1. 17. f. 8. 



