Vol. 57.] IGNEOirS EOCKS AMONG THE MALVEKX CAMBRIANS. 



167 



Fig. 7. — Portion of a phenocryst^ similar to that sketched in tecct- 

 Jtg. 6, p. 165^ hut larger^ ^y^'^y cit i^^ ^dge of the same slide as 

 that one. (X 25 diam.) 



^ 



^ ^ i9^\ ^ 



Considerable corrosiou has taken place, as seen in the upper part of the 

 diagram, and in places there is a resorbed margin. In this semidiagrain- 

 matic figure the minerals are represented as in fig. 6 ; the black is opacite. 

 The dark line at the bottom of the figure is a portion of the edge of the 

 section. 



lY. Atjgite-Basalt. 



One rock (M 101), intrusive in the Grey Shales near Martins, 

 differs both from the type just described, and from the olivine- 

 basalts. It is compact, purplish-grey, and, like the preceding type, 

 shows a fine-grained pilotaxitic (or hyalopilitic) groundmass, with 

 numerous augite-microlites and granules, and some apatite. No 

 amphibole is seen, and the only phenocrysts are numerous small, 

 pale, partly or wholly serpentinized, augites. In its greater specific 

 gravity (2*73), and probably in its lower percentage of silica and 

 alkalies, and its greater percentage of iron, lime, and magnesia (see 

 Table lY, p. 176), the rock differs from tiie andesitic camptonites, 

 and approaches the olivine-basalts ; but no olivine, or secondary 

 biotite, is present. Serpentine and calcite, and probably analcime, 

 occur among the alteration-products. 



