chap. xn. Tertiary Formation. 387 



The thirty-six species (including those collected by 

 myself and by M. d'Orbigny) are all extinct, or at least 

 unknown ; but it should be borne in mind, that the 

 present coast consists of shingle, and that no one, I 

 believe, has dredged here for shells; hence it is not 

 improbable that some of the species may hereafter be 

 found living. Some few of the species are closely related 

 with existing "ones ; this is especially the case, according 

 to M. d'Orbigny and Mr. Sowerby, with the Fusus 

 Patagonicus ; and, according to Mr. Sowerby, with 

 the Pyrula, the Venus meridionalis, the Crepidula 

 gregaria, and the Turritella ambulacrum, and T. 

 Patagonica. At least three of the genera, namely, 

 Cucullaea, Crassatella, and (as determined by Mr. 

 Sowerby) Struthiolaria, are not found in this quarter 

 of the world ; and Trigonocelia is extinct. The evidence 

 taken altogether indicates that this great tertiary 

 formation is of considerable antiquity ; but when treat- 

 ing of the Chilian beds, I shall have to refer again to 

 this subject. 



The white pumiceous mudstone, with its abundant 

 gypsum, belongs to the same general epoch with the 

 underlying fossiliferous mass, as may be inferred from 

 the sjiells included in the intercalated layers at ISTeuvo 

 Gulf, S. Julian, and S. Cruz. Out of the twenty-seven 

 marine microscopic structures found by Prof. Ehrenberg 

 in the specimens from S. Julian and Port Desire, ten 

 are common to these two places : the three found at 

 Neuvo Gulf are distinct. I have minutely described 

 this deposit, from its remarkable characters and its 

 wide extension. From Coy Inlet to Port Desire, a dis- 

 tance of 230 miles, it is certainly continuous ; and I 

 have reason to believe that it likewise extends to the 

 Kio Chupat, Neuvo Gulf and San Josef, a distance of 

 570 miles : we have, also, seen that a single layer occurs 



