Dr. G. J. Hincle — On a Neio Fossil Sponge. 23 



lines or markings radiating from a centre. These patches are so 

 numerous as in places to cover the surface, and their margins overlap 

 each other, so that their individual outlines cannot in all cases be 

 distinguished ; further, it can be seen that they are not limited to 

 a single surface layer, for the rock to the thickness of about a 

 millimetre consists of several distinct successive films or layers, 

 each covered with similar rusty patches of radiating lines. Examined 

 with a lens or under a mici'oscope, these lines are seen to be in 

 reality very fine, delicate needle-like spicules radiating horizontally 

 from a centre. The spicules are not all of the same length, so that 

 the outer margin of each patch is uneven, and the general appearance 

 of these circles impressed on the rock-surface calls to mind the 

 nimbus or halo which in old religious books is depicted round the 

 heads of saints. 



The circular patches are from 18 to 24 mm. in diameter; the 

 spicules of which they are formed are straight, simple, apparently 

 smooth, and nearly of an even thickness throughout their length, 

 "which appears to be from 8 to 10 mm., whilst they are only about 

 •035 mm. in thickness. In some instances the spicules radiate from 

 the centre of the patch, in others there is a small free central space, 

 and occasionally they are disposed in the shape of a fan. In all 

 cases the spicules form an extremely thin layer. The spicules are 

 for the most part pyritized, in some instances they are reduced to 



^\;4\l///m' 



SiepkaneUa saneta, gen. et sp. nov. ; Utica Shale (Ordovician), Ottawa, Canada. 



rusty peroxide. This change of the original silica to pj'rites and 

 peroxide of iron seems to be of very general occurrence wherever 

 siliceous sponges have been preserved in black bituminous shales ; 

 well-known instances are those in the Cambrian shales of St. Davids, 

 South Wales, and those lately described by Sir J. W. Dawson from 

 the black Ordovician shales at Metis, Lower St. Lawrence (Trans. 

 Eoy. Soc. Canada, vol. vii. 1889, p. 31). 



It may be taken for granted that each of the numerous circular 

 patches in this rock indicates the basal portion of a distinct sponge; 

 but it is hardly likely that it represents the entire skeleton of the 

 organism, and it is insufficient to determine conclusively the nature 

 of the sponge. It has been suggested by Sir J. W. Dawson,^ who 

 has seen some of the specimens, that they may be the root-spicules 

 of Hexactinellid sponges. As a rule, however, the anchoring- 

 spicules in this group of sponges consist of a more or less compact 



1 Notes on Specimens, Peter Eedpath Museum, 1888, p. 59. 



