Prof. Bonney and Miss C. Raisin—Spilites of Jersey. 59 
_ I have much pleasure in associating the name of this remarkable 
sponge with its discoverer, Sir J. W. Dawson, F.R.S. 
Distribution.—Shales of the Quebec Group, probably near the base 
of the Lévis Division, at Little Métis, Lower St. Lawrence, Province 
Quebec. 
EXPLANATION OF PLATE IY. 
Paleosaccus Dawsoni, Hinde; a portion of the mesh-work of the sponge-wall 
exposed on the surface of a slab of black shale. Reduced to + the diameter. 
From the Quebec Group (Ordovician) at Little Métis, Canada. 
TV.— On tHe So-cALLED SprLites OF JERSEY. 
By Prof. T. G. Bonnzy, D.Sc., LL.D., F.R.S., F.G.S., 
and Miss Carupriny A. Raistn, B.Sc. 
BOUT one quarter of the Island of Jersey is occupied by 
argillites or fine grits, often of a greenish grey colour referred 
by French geologists to the ‘“ Phyllades de St. Lo.” They are, 
therefore, if not equivalent to the Lower Cambrian beds of Britain, 
slightly more ancient.’ In close association with these, but accord- 
ing to Prof. de Lapparent, belonging rather to the upper part of the 
group, occur certain more or less porphyritic rocks, as to the origin 
of which different opinions have been entertained. M. Noury in his 
useful ““Géologie de Jersey” describes them under the name of 
“spilites.”’ While admitting that in many respects they exhibit the 
characters of an eruptive rock, he concludes, after an elaborate 
discussion, that they are metamorphosed argillite, the change 
being primarily due to the “porphyres pétrosiliceux;” the felspar 
crystals, however, he thinks, may be attributed to the action of the 
diorite.? Prof. de Lapparent, in a paper published in 1884, briefly 
refers to these ‘“spilites” as amygdaloidal melaphyres; and again, 
in 1891, expresses the opinion that they are igneous rocks (tufts, 
breccias, etc.), calling them porphyrites.° But as the point is one 
of considerable interest, the notes and conclusions arrived at in 
the summer of 1888, by one of the writers, may be worth placing 
on record. 
A few words are needed to explain the delay and the joint 
authorship of this paper. Prof. Bonney in 1888 had the advantage 
of spending a week in Jersey in company with the Rev. H. Hill, 
who has added so much to our knowledge of the Channel Isles.’ 
They examined with some care the mass of “spilite” at Mont 
1 Bull. Soc. Géol. de France, vol. xvi. p. 412, A. Bigot; and Bull. du Lab. de 
Géol. de la Faculté des Sciences de Caen., A. Bigot, December, 1890, p. 11. 
* Géologie de Jersey, 1886, M. Noury, pp. 49, 61, 63. 
8 Bull. Soc. Géol de France, 1884, tome xii. p. 288; Q.J.G.S., 1891, vol. xlvii. 
p- 36; Comptes Rendus, 1890, vol. 111, p. 543. After the completion of the 
manuscript of this paper, we received a copy from Prof. de Lapparent of his newly 
published ‘‘ Note sur les Roches Eruptives de l’Ile de Jersey’’ (Ann. de la Soe. 
Scientif. de Bruxelles, tome xvi. 2° partie) in which these ‘‘spilites’’ are described. 
But as he refers chiefly to other quarries and enters on the whole into fewer 
details than we have done, the results of our work may be still of some little 
interest, at any rate to English readers. 
4 Q.J.G.S. 1884 vol. xl. p. 404; Q.J.G.S. 1887 vol. xlii. p. 322; Q.J.G.S. 1889 
vol. xlv. p. 380; Q.J.G.8, 1892 vol. xlviil. p. 122. 
