﻿278 



DR. A. HOLMES ON THE TEUTIARY 



[vol. lxxii, 



arduous task I am particular^ grateful. Finally, I owe my thanks 

 to Mr. Gr. S. Sweeting, who kindly cooperated with me in the 

 preparation of the photomicrographs reproduced in Plates XX 

 A XXI. 



EXPLANATION OP PLATES XX & XXI. 

 Plate XX. 



Fig. 1. Solvsbergite (153) found between Miali and the Sanhuti River, Mozam- 

 bique. Chief minerals : anorthoclase, cossyrite, and soda-pyroxenes. 

 X 20. (See p. 233.) 



2. iEgirine-trachyte (152) north of Sokoto Hill. Chief minerals : anortho- 



clase, cossyrite, and segirine. X 20. (See p. 235.) 



3. Phonohte (150) near the Sanhuti River. Chief minerals : anorthoclase, 



nepheline, natrolite, soda-pyroxenes, and amphiboles. The dark 

 phenocryst is cossyrite surrounded by a green chlorite-like mineral. 

 X 20. (See p. 236.) 



4. Basalt with ophitic patches (156) near the Sanhuti River. Chief 



minerals: labradorite and augite, with some palagonite in the ground- 

 mass. X 20. (See p. 241.) 



5. Picrite-basalt (155) near the Sanhuti River.. Chief minerals : purple 



augite and olivine ; labradorite, purple augite, and glass in the 

 ground-mass. X 20. (See p. 244.) 



6. Micro-vesicular basalt (128) from a sill at the western base of Sokoto 



Hill. Chief minerals : labradorite and augite, in a base of dark-brown 

 glass. The vesicles are occupied by chalcedony and chlorite. X 20. 



Plate XXI. 



Fig. 1. Basalt (141) from the dyke at Mochelia. Chief minerals : labra- 

 dorite and augite in a base of dark-brown glass. X 36. (See 

 p. 246.) 



2. Amygdaloidal sandstone (112) from contact with the Mochelia dyke 



(text-fig. 5). Grains of quartz, orthoclase, and microcline are present 

 in the sandstone, cemented by calcite which is replaced near the dyke 

 by opal. In the steam-holes opal, chalcedony, and quartz are present. 

 X 12. (See p. 249.) 



3. Amygdaloidal basalt (124) south of the Monapo River. Chief minerals : 



labradorite and augite in a base of dark-brown glass. X 20. (See 

 p. 250.) 



4. Amygdale in amygdaloidal basalt (136) east of Murimatigri Quartel. 



Illustrating the replacement of heulandite (dark areas) by chal- 

 cedony. X 20. (See p. 252.) 



5. Hornblende-andesite (126) from a dyke penetrating amygdaloid south 



of the Monapo River. Chief minerals : andesine, hornblende, and 

 biotite, in a ground-mass consisting of the same minerals, together 

 with quartz and orthoclase. X 20. (See p. 256.) 



6. Pyroxene-andesite (144) found near the Monapo River. Chief 



minerals : andesite. augite, and hypersthene, in a ground-mass of 

 hyalopilitic texture. X 20. (See p. 259.) 



. Discussion. 



Mr. F. P. Messell said that he had listened to the paper 

 with the greater interest, in that he had spent more than ten years 

 in a neighbouring part of Africa. He was quite in accord with 



[November 23rd, 1917.] 



