398 W. J. Sollafi — A New Cretaceous Sponge. 



present to which this vegetation was due was interrupted by in- 

 tervals of intense glaciation, as it is suggested was the case during 

 the Eocene and Miocene periods in Switzerland and Italy, Professor 

 Nordenskiold has been unable, in successive visits to Spitzbergen, to 

 discover in the well-exposed and thick succession of Miocene deposits 

 of that island, so rich in plant-remains, any traces of a bed presenting 

 evidence of ice-action.^ 



{To be continued in our next Number.) 



11. — On Eubrochus clausus, a Yitreo-hexactinellid Sponge 

 FROM THE Cambridge " Coprolite " Bed. 



By W. J. SoLLAS, B.A., F.G.S., Assoc. E.S.M. 



(PLATE XIY.) 



AMONG-ST the undescribed sponges from the Cambridge " Copro- 

 lite " bed, which have come under my notice, is the beautiful 

 hexactinellid that forms the subject of this communication. 



An almost complete specimen and a well-preserved fragment of 

 the sponge are to be seen in the Woodwardian Museum ; a good 

 specimen has been placed in the Geological Survey Collection by 

 Mr. Jukes-Browne ; and I once saw another in the cabinet of Mr. 

 Buxton, Trin. Coll., Cambridge. Besides these, I have only met 

 with a few smaller fragments, and thus the species would seem to be 

 somewhat a rare one. 



PL XIV. Fig. 1 represents the specimen in the Woodwardian 

 Museum, natural size ; outwardly it resembles a short stout club, or a 

 vase in which the sides have curved together so as to obliterate the 

 mouth, and thus to form a continuous roof over the cavity they inclose. 

 Mr. Jukes-Browne's specimen is very similar to this ; but a short 

 process (Fig. 2 c), diverging from the summit, seems to indicate that 

 his was a branching form, while the Museum specimen is certainly 

 single. 



The bases of the specimens are somewhat worn, so as to make it 

 impossible to determine whether the sponge was sessile or not in 

 habit. 



The surface is covered with a network of fine linear depressions, 

 looking like narrow grooves scored into the substance of the 

 phosphatic material of which the fossil is composed. These lines 

 are the inner half of hollow casts, the outer half of which has been 

 worn away by gentle attrition on the sea-floor, and they represent 

 the fibrous network which once constituted the dermal skeleton of 

 the sponge. The network thus indicated covers not only the sides 

 of the fossil, but its summit also, completely surrounding it, like 

 the net which incloses a balloon. 



Its constituent fibres cross one another approximately at right 

 angles, and so form a square meshwork, which closely resembles 

 that of Farrea occa (Fig. 3). The centres where the fibres cross 

 and fuse into one another are -yoo of an inch apart on the average, 



1 Geol. Mag. 1876, Decade II. Vol. III. p. 266. 



