400 Sorace B. Woodward — On the Metamorphism of Strata. 



*^54:. Cardnim, sp. 



A small distinctly ribbed form, not determinable. Winkler, p. 203. 

 55 Cardium (Serripes) Groenlandicum, Chem., var. 



Cardiiim Groenlandicum, Wood, tab. 3, fig. la, Winkler, p. 202. 

 Serripes Grmnlandicus, Chem., Morch, Payk. 



Eatlier common, long. 42 mm. ; alt. 35 mm. circ. 

 Spm. jun. „ „ 9 „ „ 8 „ 



This variety looks most like to the variety from Spitzbergen, 



called C. Fabricii by Deshayes. 

 Old specimens are rather diiScnlt to distinguish from Mactra 

 without the hinge. The Mactra is, however, easily recognized 

 by the want of the impressed lines for the reception of the ex- 

 ternal ligament of Cardium. 

 66 Modiolaria nigra, Gray. 



The nucleus of a rather large specimen. 



57. Mytiliis edulis, L. 



A few young specimens, the largest 32 mm., from Paykull. 



58. Mytilus hesperianus. Lam., Wood. 



Mytilus densatus. Wood, Cat. 

 Tungubakkar paa Tjornees. The largest specimen is 80 mm. long 

 and 35 mm. high. 



59. Lepralia auricidata. Hen., Smitt. 



60. Balanus sulcatus, Brug. 



61. Balanus ovularis, Lam. ? 



IV. — Notes on Metamorphism of Strata in the Mendip Hills. 



By Horace B. Woodward, F.G.S., 

 of the Geological Survey of England. 



ALTHOUGrH the Mendip Hills have received a large share of 

 attention from geologists since the beginning of the present 

 century, and ^particularly from Buckland and Conybeare, Weaver, 

 De la Beche, Eamsay, and Moore, there are still many points of 

 great interest that require to be worked out. 



The object of the present communication' is to re-direct attention 

 to some instances of silicification which are to be met with in certain 

 formations on the Mendip Hills, and to offer some theoretical re- 

 marks on the origin of this metamorphism. 



General Description. — On Harptree and Egar Hills, in the neigh- 

 bourhood of Chewton Mendip, and also near Emborrow, reposing on 

 the Dolomitic Conglomerate, the Mountain Limestone, and the Old 

 Eed Sandstone, there occurs a peculiar siliceous deposit. In the 

 upper part it is a compact chert containing shells, lower down come 

 sandy beds ; sometimes the chert appears conglomeratic, or rather 

 brecciated, for the fragments contained in it are angular. The entire 

 deposit must attain in places a thickness of 30 feet, but in the 



^ I should mention that my observations -were made in 1868 and 1869 when 

 engaged with my colleagues, Messrs. W. A. E. Ussher and J. H. Blake, in re- 

 surveying the Mendip Hills, under the superintendence of Mr. H. W. Bristow, 

 F.E.S. 



