220 A, WM. Finlayson—Petrology of Huelva, Spain. 
Fic. 7. Homalonotus ascriptus, sp. nov. Head-shield. x 23. 
» 8. Ditto. Hypostome. x 8. 
» 9. Beyrichia (Ceratopsis) duftonensis, sp.nov. Left valve. x 10. 
», 10. Ditto. Right valve. x 10. 
peel) a eDitto, dithonmescalOs 
», lla. Side-view of same. x 10. 
,, 12. Beyrichia (Tetradella) Turnbulli, sp. noy. Left valve. x 10. 
,, 12a. Ditto, ditto. Impression of surface of same. x 10. 
>, 13. Ditto, ditto: x 10: 
,, 13a. Ditto, ditto. Impression of surface of same. x 10. 
», 14. Beyrichia (Ctenobolbina ?) superciliata, sp. nov. Left valve. x10. 
», 14a. Ditto, ditto. Impression of surface of same. x 10. 
(Zo be continued.) 
IV.—Perrrotocy anp Srrucrure or tar Pyriric Fiery or Huvetva, 
Sparn. 
By A. Monerierr Finuayson, M.Sc., F.G.S., 
Assoc. Inst. Min. Met., Assoc. Otago School of Mines. 
(PLATE XVIII.) 
Inrropucrion. 
(J\HE great copper-mining district of Southern Spain and Portugal 
has been studied by several eminent geologists, and the problems 
presented in the geology of the field and of its ore-deposits have given 
rise to conflicting opinions. The three most debated points have been 
the origin of the ore-deposits, the relations of the igneous rocks, and 
the age of the sedimentary formations. The present paper, the field- 
work for which was carried out during the last summer season, deals 
in the main with the two latter points, and the writer takes this 
opportunity of expressing his indebtedness to Professor W. W. Watts 
and to Dr. C. G. Cullis for their advice and suggestions during the 
subsequent petrological studies at the Imperial College of Science and 
Technology, London. 
GENERAL RELATIONS oF THE DisrrRict. 
The copper-belt is situated at the southern end of the Iberian 
meseta, a fractured tableland whose essential rocks are of Paleozoic 
age. The meseta received its present structure with the tectonic 
movements and igneous eruptions of late Carboniferous and Permian 
times, and is one of the old Hercynian fragments, like the Armorican 
Mountains, the Central Plateau of France, the Vosges, and other 
districts of Europe. The axes of folding trend generally east and 
west, and the movements were accompanied by widespread intrusions 
of igneous rocks, and by the formation of many of the most important 
ore-deposits of the peninsula. The Hercynian disturbances were closed 
by extensive fracturing round the present edges of the tableland, 
notably along its south-east border. Thus the valley of the Guadal- 
quivir follows the line of the insinking created at this period. This. 
great fault cuts off the old mass across the strike of the folds, and is 
marked by a well-defined scarp along the edge of the valley between 
Seville and Cordoba. The fault-line appears to pass westward from 
the lower Guadalquivir, along the south coast by Huelva and the 
