59i REPORT 18C3. 



Page. Plate. Fi?. 



70. II. 4. Mya Montereyana, Conr., p. 313. [Figure resembles Periploma 



aryentaria.~] Monterey Co. 



5. ?Alya8ul,stmiata,Conr. [Comp.Macomainqmnata.'] Monterey Co. 



}) n 6. Arcopagia medialis, Conr., p. 314. Like A. biplicata, Conr.. of 



the Maryland Miocene. [Closely resembles Lutricola alta, Conr.] 



Montere Co. 



,, 7. Tapes liuteahim, Conr., p. 314. California. 



1 



8. Area canal-is, Conr., p. 314. Santa Barbara, 

 9. Area trilincata, Conr., p. 314. Santa Barbara. 



;onr., p. dl4. Uamorma. 



ensis, Conr. [Closely resembles Pect. intermedms.~] 



i, Ccrnr., p. 313. ? Santa Barbara and shores of 



10. Area congesta, Conr., p. 314. California. 



71. III. 11. Axincea llarbarensis, 

 12. Mulinia densata, 



Pablo Bay. 



Dosinia I'.mgula, Conr., p. 315. Monterey. 



13. Dosinia alta, Conr., p. 315. Monterey. 



14. Pecten Pabloensis, Conr. San Pablo Bay. 



15. Pallium Estrellanum, Conr., p. 313. Estrella Valley. 



' 16. Janira Mia, Conr., p. 312. Santa Barbara. 



/2 ' ^ I7a } Ostrea Titan > Conr v p kil. Proc - 1856 - San Luis Obispo. 



73. V. 25. Pandora bilirata, Conr., p. 267. [Closely resembles Kennerlia 



bicarinata.~\ Santa Barbara. 

 24. Cardita occidental, Conr., 1855, p. 267. [?= C. ventricosa, Gld.l 



Santa Barbara. 

 23. Diadora crucibuliformis, Conr., 1855, p. 267. [? = Pundweila 



cueidlata, Gld.] Santa Barbara. 



Fossils of Gatun, Isthmus of Darien. 



72. V. 22. Malea ringens, Swains. Gatun. 

 19. TurriteUa altilira, Conr. Gatun. 



20. Turritella Gatunensis, Conr. Gatun. 

 n 20. Triton, sp. ind. Gatun. 



n 21. ? Cytherea Dariena, Conr. [The figure does not appear conspe- 

 cific with that in the Blake collection, no. 50.] Galun. 



The northern fossils are supposed by Mr. Conrad to be of the Miocene period, 

 and not to be referable to existing species. Those from Sta. Barbara, however, 

 are clearly of a very recent age, and probably belong to the beds searched by 

 Col. Jewett. But by far the most interesting result of Dr. Newberry's ex- 

 plorations was the discovery of the very typical Pacific shell, Malea ringens, 

 in the Tertiary strata on the Atlantic slope of the Isthmus of Darien, not 

 many miles from the Caribbean Sea. The characters of this shell being such 

 as to be easily recognized, and not even the genus appearing in the Atlantic, 

 it is fair to conclude that it had migrated from its head waters in the Pacific 

 during a period when the oceans were connected. We have a right, there- 

 fore, to infer that during the lifetime of existing species there was a period 

 when the present separation between the two oceans did not exist. We 

 may conclude that species as old in creation as Malea ringens may be found 

 still living in each ocean ; and there is, therefore, no necessity for creating 

 " representative species," simply because, according to the present configu- 

 ration of our oceans, we do not see how the molluscs could have travelled to 

 unexpected grounds. 



100. In vol. vii. of the Pacific Railroad Reports, part 2, is the Geological 

 Report, presented to the Hon. Jefferson Davis, then Secretary of War, by 

 Thos. Antisell, M.D. He states reasons for believing that during the Eocene 

 period the Sierra Nevada only existed as a group of islands ; that its final 

 uplifting was after the Miocene period ; and that during the whole of that 



80 



