EAGADINIA. 83 



ring-like swellings near their centres, and at their distal ends split up irregularly 

 into small twigs, by which they are interlocked together, but they do not appear to 

 form prominent nodes at the point of junction of the arms. The outer surface of 

 the sponge, where the dermal layer is not present, shows, under a strong lens, the 

 tubercled spicular arm projecting outwards. The body-spicules of this species are 

 exactly similar to the detached spicules discovered in the Trimmingham Chalk by 

 Professor Sollas *, and named by him Compsapsis cretacea, and in the Chalk flint at 

 Horstead by myself, and named Ragadinia annulata f . As, however, these remarkable 

 body-spicules are not peculiar to a single species of sponge, the names given to the 

 detached spicules cannot be applied to the present or the following forms in which 

 they occur. 



A dermal layer is present in some portions of the outer surface of the specimens, 

 and probably originally extended over the entire sponge. It is composed of the 

 horizontally expanded heads of shafted spicules, about '3 mm. in width, which are 

 deeply lobed and laciniated. These heads overlap each other so as to form a con- 

 nected membrane with a smooth surface. Some of the detached dermal spicules 

 from the Horstead Chalk flint J, which I referred to Ragadinia annulata, probably 

 belong to the present species. These dermal spicules also very closely resemble 

 those of the existing Corallistes asterodiscus, O. Schmidt ; but from an examination 

 of microscopic specimens of this sponge, labelled by Schmidt himself, T have ascer- 

 tained that its body-spicules are different from those of the present species. 



Distribution. Upper Chalk : Oare, Huish, Wiltshire {Cunnington coll.). 



Eagadinia sulcata, Hinde, n. sp. (Plate XX. figs. 1, 1 a.) 



Sponges cup- or funnel-shaped, frequently with only a shallow interior depression. 

 They gradually taper to a short, straight or oblique, cylindrical stem, with root-like 

 processes at its termination. Sometimes there are small nodose projections near the 

 rounded margins of the cup. The walls of the cup vary from 6 to 8 mm. in 

 thickness. The specimens are from 70 to 90 mm. in height and about 55 mm. in 

 width at the summit. 



Both the outer and inner surface of the sponge is traversed by numerous open 

 canals, about "5 mm. in width, frequently disposed side by side, and running in an 

 oblique direction, thus giving the surface a furrowed aspect. In addition to the 

 surface-canals there are others extending into the wall and apparently opening into 

 the surface-canals. 



The interior spicular skeleton is composed of spicules of the same annular cha- 

 racter, but larger than those of Ragadinia compressa ; mingled with these there are 



• Annals & Mag. Nat. Hist. 5th ser. vol. vi. 1880, p. 387, pi. 19. figs. 21, 22. 

 t Fossil Sponge-Spicules, 1880, p. 58, pi. 5. figs. 1-4. 

 X Fossil Sponge-Spicules, pi. 4. figs. 24-30. 



m2 



