542 PROF. W. J. SOLLAS ON SOME FOSSIL SPONGES 



canal system with the Hexaetinellid PorocypeUia, the Lithistid 

 Siplionia, and an imdescribed B-enierid sponge. It differs from 

 Porocypellia in the imperforate character of its nodes and in the 

 absence of a stanrodermal covering. 



Emploca ovata, sp. nov. (Plate XX. figs. 1-6.) 



The species is founded on two well-preserved specimens, one of 

 which is ovate in form, 1| inch high and j inch broad ; the other, 

 more cylindrical, also 1| inch high, but 1J inch in breadth. In 

 both, the incurrent ostia are about -A- inch in diameter, and the 

 osculum | inch. Both are sessile, a scar near the base indicating 

 the point of attachment. The nearest approach I can find to this 

 form amongst described species is Seypliia radiata ovalis, Quenst., 

 from the White Jura (d) of Heuberge, near Balingen. It also 

 resembles Scyphia dictyota, Gold!'., from the Jurassic limestone of 

 Streitberg. 



Log. Dundry Hill, Bristol. 

 Hor. Upper part of A. Humj)7iriesianus-zone. 

 Obs. The simplicity of the skeletal nodes is a character which 

 cannot be mistaken in the thin slices of the sponge which I have 

 examined under the microscope; but the presumed absence of a 

 continuous dermal skeleton rests chiefly on negative evidence. Con- 

 sidering, however, the excellent state of preservation of the speci- 

 mens which have been examined, one would have certainly expected 

 to find some traces of such a dermal covering if it had originally 

 been present. 



Mine red Char ciders. The originally siliceous skeleton, in this as 

 in all the sponges described in this paper, now consists of colourless 

 transparent caleite, except where, as near the surface, it is repre- 

 sented merely by hollow casts or moulds lined with a thin crust of 

 some red ferruginous material. The material filling up the meshes 

 of the skeleton is chiefly calcareous, and evidently owes its origin 

 to a very fine calcareous mud, which has since become converted 

 into stone by a deposition of caleite. The caleite in some places 

 (1) has been evenly distributed throughout the mud, and so pro- 

 duced an apparently homogeneous, finely granular, whitish-grey 

 opaque material ; in others (2) it has gathered along certain lines 

 so as to form a network, the minute meshes of which are filled with 

 an opaque granular material like that in (1) ; finally, in others (3) 

 it has entirely obliterated the original granular character of the 

 mud and brought it into the same crystalline condition as itself; 

 thus patches of colourless caleite are produced. The matrix can 

 be traced continuously from one place, where it is in a condition 

 like that described in (1), through others by which it passes through 

 all stages up to (3), that of complete crystallization. The network 

 formed by the absence of mud or concentration of caleite along 

 certain curved lines, as in (2), has a remarkably organic appearance, 

 simulating in some cases Hexaetinellid structure so closely as almost 

 to lead astray the observer, the more so that it is frequently in 

 direct continuation with the calcitic replacement of genuine Hexacti- 



