86 Mr, J. S. Bowerbank on Moss Agates 



Australian species, although it differs from it in having a 

 bolder form of vessel. The occurrence of this minute and 

 beautiful tissue in the fossil state, and its perfect accord- 

 ance in structural character with the recent types, afford the 

 most indisputable evidence of the animal origin of the fibrous 

 structures inclosed within the bodies that are under consider- 

 ation. The tissues which we have just described are not the 

 only vascular structures that are to be found in these interest- 

 ing remains. Upon examining the great central cavity of the 

 sponge-fibre represented by PL III. fig. 2, at the point a } with 

 a power of 120 linear, there is a dark spiral thread or line seen 

 passing down the surface of the cavity for a considerable di- 

 stance ; and when this is examined with a power of 500 linear, 

 it assumes the appearance of a spiral tubular thread, frequently 

 obscured by irregular patches of what appears to have been a 

 glutinous animal matter. In another specimen of green jasper 

 in which this curious tissue occurs, and which is represented 

 by PL III. fig. 6, its spiral course is much less obscure, and 

 when examined with a microscopic power of 800 linear its tu- 

 bular nature is evident. The same structure is also seen lining 

 the cavity of almost every fibre of the sponge in the specimen 

 of green jasper that I have before described as having its 

 structure arranged in foliaceous plates, like the skeletons of the 

 leaves of some endogenous plants. 



Another exceedingly remarkable tissue occurs in a moss 

 agate which is probably from Oberstein. In this specimen 

 the sponge-fibre differs materially from any other that I have 

 met with in the fossil state. It is arranged in the same com- 

 plex mode that we observe in the sponges of commerce ; but 

 the fibre is exceedingly large, and appears to have been sur- 

 rounded by a villous coat. It has either been furnished with 

 a cavity whose size has been but very little less than its ex- 

 ternal diameter, or it has had a solid fibre like the greater 

 number of the recent keratose sponges ; but it is exceedingly 

 difficult to decide under the present circumstances which form 

 of structure it was that prevailed previous to its becoming 

 fossilized. In cutting and polishing the specimen, half or a 

 third of the substance of some of the fibres have been removed, 

 so as to afford clear sections of them in a longitudinal direc- 

 tion ; and wherever this has occurred, there are one or two mi- 

 nute vessels to be seen nearly in the centre of the fibre, run- 

 ning in the direction of its axis. These vessels are uniform 

 in diameter and simple in their structure, and but very rarely 

 dividing or sending off a branch. Within these vessels, at in- 

 tervals, there are pellucid round globules, which entirely fill, 

 or very nearly so, their internal diameters, as seen in PL III. 

 fig. 7* The vessels represented in this case are from the 



