Vol. 58.] JASPERS OF SOUTH-EASTERN ANGLESEY. 433 
I fear there is not much hope that any organisms existing therein 
can have escaped effacement. 
The indirect evidence here set forth, however, seems to me so 
strong as to leave little doubt that the jaspers of Anglesey 
are of organic origin, and that they are really altered 
radiolarian cherts. 
That jaspers, whether associated with igneous rocks or not, 
should occur in connection with limestones, is only to be expected : 
and in the limestones, accordingly, we constantly find them, in all 
the three areas here described. As before remarked, they occur here 
generally in small irregular aggregates; but in a limestone north- 
east of Garth Ferry, on the Beaumaris road, there is a thin bed of 
jasper some yards long. Both these forms are, as is well known, 
characteristic of chert and flint in the Carboniferous Limestone and 
the Chalk. It is interesting to recall that, so long ago as 1888, 
the Rev. J. F. Blake wrote in his ‘ Monian System ’! of limestones 
in the central region of the Island :— 
‘ There are bands and isolated pieces of red jasper, which behave towards the 
limestones exactly as flint does to chalk, and a similar origin is at least suggested.’ 
I have not yet visited the spot referred to, but the rocks described 
are clearly the same as those of the south-east. In that remark, 
therefore, written 14 years ago, the Rev. J. F. Blake has anticipated 
the most important result arrived at in this paper. 
To recapitulate: radiolarian cherts, sometimes altered to jasper, 
are intimately associated with, and fill interspaces in, pillowy 
diabase-lavas in the South of Scotland. The same association has 
been observed in several other parts of the world, and at horizons 
ranging from the Lower Ordovician to the Cretaceous. 
The mode of occurrence of the Anglesey Jaspers is similar, 
even in small details, to that of the cherts of the South of Scotland,” 
and it seems reasonable, therefore, to regard them as of similar 
origin. 
‘Variolite, in the typical locality of Mont Genevre, occurs in a 
diabase with the same pillowy structure as that possessed by the 
rocks so frequently associated with jaspers and cherts. It has 
actually been found in such at Point Bonita, but is there very rare. 
The Anglesey phenomena are therefore remarkably well developed ; 
and the occurrence here of limestone also, completes, in a certain 
sense, the circle of associations. 
LY. AcE anp Externat RELATIONS. 
This part of the subject falls under two heads :—(1) The relation 
of the group to the fossiliferous rocks; and (2) Its relation to the 
crystalline schists of the district. 
* Quart. Journ. Geol. Soc. vol. xliv (1888) p. 489. 
* The only direct evidence that the Anglesey diabases are true lavas is the 
occurrence of the thin tuffs. But the infillings of jasper could hardly find their 
way into an intrusive rock, until after considerable denudation. 
