376 Tertiary Formations. part it. 



three main beds, of which the uppermost is thin, and 

 consists of ferruginous sandstone, with many shells of 

 the great oyster and Pecten Paranensis ; the middle 

 bed (E) is a yellowish earthy sandstone abounding with 

 Scutellee; and the lowest bed (F) is an indurated, 

 greenish, sandy clay, including large concretions of 

 calcareous sandstone, many shells of the great oyster, 

 and in parts almost made up of fragments of Balanidas. 

 Out of these three beds, I procured the following twelve 

 species, of which the two first were exceedingly numerous 

 in individuals, as were the Terebratulee and Turritella3 

 in certain layers : — 



1. Osfrea Patagonica, d'Orb. ' Voyage Pal.' (also at St. Fe and 



whole coast of Patagonia). 



2. Pecten Paranensis, d'Orbig. do., and PL III. f . 30 of this work 



(St. Fe, S. Josef, Port Desire). 



3. Pecten centralis, G. B. Sowerby, PI. III. f. 31 (also P. Desire 



and S. Cruz). 



4. Pecten geminatus, do., PI. II. f. 24. 



5. Terebratula Patagonica, do , PL II. f. 26 and 27 (also S. Josef). 



6. Struthiolaria ornata, do., PI. IV. f. 62 (also S. Cruz). 



7. Fusus Patagonicus, do., PI. IV. f. 60. 



8. Fusus Xoachinus, do., PI. IV. f. 58 and 59. 



9. Scalaria rugulosa, do., PI. III. f. 42 and 43. 



10. Turritella ambulacrum, do., PI. III. f. 49 (also S. Cruz). 



11. Pyrula, cast of. like P. ventricosa of Sowerby, Tank Cat. 



12. Balanus varians, G. B. Sowerby, PI. II. f. 4. 5, 6. 



13. Scutella, differing from the species from Xuevo Gulf. 



At the head of the inner harbour of Port S. Julian, 

 the fossiliferous mass is not displayed, and the sea-cliffs 

 from the water's edge to a height of between 100 and 

 200 feet are formed of the white pumiceous mudstone, 

 which here includes innumerable, far-extended, some- 

 times horizontal, sometimes inclined or vertical laminae 

 of transparent gypsum, often about an inch in thick- 

 ness. Further inland, with the exception of the 

 superficial gravel, the whole thickness of the truncated 

 hills, which represent a formerly continuous plain 950 

 feet in height, appears to be formed of this white mud- 



