560 Valley of Copiapo. pakt n. 



was, in a marvellously short horizontal distance, after 

 frequent alternations, replaced by it. When this 

 occurred, a mountain-mass, several thousand feet in 

 thickness, was thus composed ; the black calcareous 

 shale-rock, however, always included some layers of the 

 pale-yellowish siliceous sandstone, of the red conglome- 

 rate, and of the greenish jaspery and pseudo-honestone 

 varieties. It likewise included three or four widely 

 separated layers of a brown limestone, abounding with 

 shells immediately to be described. This pile of strata 

 was in parts traversed by many veins of gypsum. The 

 calcareous shale-rock, though when freshly broken quite 

 black, weathers into an ash-colour; in which respect 

 and in general appearance, it perfectly resembles those 

 great fossiliferous beds of the Peuquenes range, alterna- 

 ting with gypsum and red sandstone, described in the 

 last chapter. 



The shells out of the layers of brown limestone, in- 

 cluded in the black calcareous shale-rock, which latter, 

 as just stated, replaces the white siliceous sandstone, 

 consist of — 



Pecten Dufreynoyi, d'Orbig. ' Voyage, Part. Pal/ 

 Turritella Andii, do. 



Eelations given in the list from Coquimbo. 



Astarte Darwinii, E. Forbes, PL V. figs. 22, 23. 

 Grypha?a Darwinii, do. PL V. fig. 7. 



An intermediate form between G. gigantea and G. incurva. 



Gryphasa, nov. spec. ? do. PL V. figs. 8 and 9. 

 Perna Americana, do. PL Y. figs. 4, 5, 6. 

 Avicula, nov. spec. 



Considered by ilr. G. B. Sowerby as the A. echinata, by M. 

 d'Orbigny as certainly a new and distinct species, having a Jurassio 

 aspect. The specimen has been nnforttmately lost. 



