420 



PROCEEDINGS OP THE GEOLOGICAL SOCIETY. [JunO 18, 



obtained the following proportions for three granites, one from 

 Egypt, and the other two from the Yosges : — 



Granite. 



Quartz. 



Orthoclase. 



Oligoclase. 



Black Mica. 



Eed Granite of Egypt 



44 



43 



9 



4 



Vosffes, Tholv 



52 



45 



2 



1 





Vosffes 



60 



28 



7 



5 





The per-centage of quartz in these granites appears very great, and 

 to vary much in quantity. The granite of Leinster contains — 



Leinster Granite. 



Quartz 27'66 



Mixed felspar (tersilicated) . . 52-94 



White mica 14-18 



Black mica 5-27 



100-05 



3. On a Stalk-eyed Crustacean /rom the Carboniferous Strata near 

 Paisley. By Thomas H. Huxley, Esq., F.E.S., Sec. G.S., &c. 



In a paper published in the Geological Society's ' Journal' (vol. xiii, 

 p. 363, 1857), I described several specimens of a Stalk-eyed Crus- 

 tacean, from rocks of Carboniferous age, to which I applied the 

 generic name of Pygocephalus, referring the genus to either the 

 Decapodous or Stomapodous group of the Class. 



My friend and colleague, Mr. Geikie, E.G.S., has been so good as 

 to draw my attention to what I believe to be another specimen of 

 the same Crustacean, obtained by the Eev. Mr. Eraser, M.A., from 

 one of the coal and ironstone mines in the Strath of the Clyde, about 

 two miles from Paisley, in dark shale*, and, by the obliging permission 

 of its owner, has placed it in my hands for examination and descrip- 

 tion. I say, I believe the new fossil to be another specimen of 

 Pygocephalus, because, in consequence of the different position in 

 which the present specimen is imbedded in the matrix, a strict 

 comparison with the others is almost impossible; and my deter- 

 mination is based rather on general analogy of the forms than on 

 a complete identification. 



While the other specimens presented a view of the ventral sur- 

 face, this shows the lateral aspect of the animal, exhibiting a side- 

 view of the carapace, of the thoracic and some of the cephalic ap- 

 pendages, and of the large and curved abdomen. The carapace, the 

 lateral surface of which is convex from above downwards, is narrow 



^ " This dark shale," says Mr. Eraser, in a letter to me, " is about 19 fathoms 

 below the surface. The ironstone-clay-band lies about 7 fathoms above it ; and 

 36 fathoms beneath it, occurs what is known here as the Hurlet or Nitshill Coal." 



