TF. J. Sollas — A New Cretaceous Sponge, 401 



the specimen whicli Mr. Jukes-Browne had collected for the Survey, 

 and which he had kindly lent me. Two transparent slices were 

 prepared from this, one cut along the length of the fossil and the 

 other at right angles across it ; both showed the hexactinellid net- 

 work in the form of empty hollow spaces in the solid coprolite ; the 

 original fibres of the skeleton have completely disappeared, leaving 

 behind mere empty casts, which are sometimes perfect sexradiate 

 spaces, and at others have entirely lost their original shape, and 

 show no trace of the form on which they were modelled. PI. XIV. 

 Fig. 2 is a sketch of the longitudinal section, natural size; in 

 colour it is light brown, but greenish where glauconite has per- 

 meated it near the exterior ; transparent, especially so along the 

 edges, but with opaque patches in its midst, probably consisting of 

 the chalky silt in which the sponge was at one time imbedded. The 

 part marked ' a ' is coprolite which has incrusted the original fossil, 



* 6 ' is the main body of the sponge, and ' c ' a process or bud 

 which has sprouted out from one side above. The network of the 

 exterior, which completely incloses the sponge, is indicated at the 

 sides ' Z ' ' Z ' by notches, which are empty or filled with phosphatic 

 material stained by glauconite. At the top the coating of coprolite 

 has better preserved the outer meshes, and so along the line ' ^ ' to 



* e ' these are well exhibited as an interrupted series of hollow sex- 

 radiate casts. At ' ^ ' the centre of one of these sexradiates may 

 be seen to give off a radius which passes to the centre of a second 

 inner sexradiate element (Fig. 4 a) ; this alone indicates clearly that 

 the skeleton of the sponge did not consist of a single layer of mesh- 

 work merely, and j)oi^ts moreover to a connexion between the 

 dermal reticulation and that interior network which we shall now 

 show Euhrochus to have possessed. Throughout both the longitu- 

 dinal and transverse sections open spaces occur, which in some 

 places are without definite form, but at others appear as clusters of 

 distinct hollow sexradiate casts (Fig. 5). They are not scattered at 

 random, but arranged along certain irregular curved lines, which 

 appear to radiate from the base of the sponge upwards, in such a 

 manner as would result if the sponge in growing left the exterior 

 network of one stage to become the interior of the next. The sex- 

 radiate casts are in all cases simple, and never complicated by the 

 addition of the characteristic octahedral 'lantern' which surrounds the 

 ' knots ' in Myliusia Grayi and in the Ventriculites.^ Thus EubrocJius 

 was evidently a solid sponge provided with an interior skeleton of 

 the same simple structure as its superficial reticulation. 



In the sections we have just described appear also a number of 

 simple acerate spicules i^o-" to -rio" long (PI. XIV. Fig. 7), and cer- 

 tain serpentine bodies, which are more like contort spicules than 

 anything else ; but their irregularity in form, occasional branching, 

 and variation in size, seem to show they are not so (see PI. XIV. Figs. 

 8, 9, 10). As to their real nature I am ignorant, as I am also of that 

 of certain minute round bodies which occur with them. The round 

 bodies are almost perfect spheres, hollow, with a circular foramen ; 

 ^ H. J. Carter, F.E.S., Ann. and Mag. Nat. Hist. ser. 4, vol. xvi. p. 76. 



DECADE II. — YOL. III. — NO. IX. 26 



