591 REPORT— 18C3. 



Page. Plate. Fig. 



70. II. 4. My a Mmitereyana, Conr., p. 313. [Figure resembles Perij^lortia 



argentarlaJ] Monterey Co. 



jf „ 5. ?31i/a siibsvniafa, Com: \^Com^. Mncoinaijiguinafa.l ^lonterey Co. 



ff ff 6. Arcopfif/ia ntedialis, Conr., p. 314. Like A. hiplicata, Conr., of 



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



Monterey Co. 



fj ff 7. Tapes linteafwn, Conr., p. 314. California. 



„ „ 8. Area canalis, Conr., p. 314. Santa rinrbara. 



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



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



Arinaa Jiarbarensis, Conr. [Closely resembles Fed. mfenmdmfi.'] 



Mulmia densata, Conr., p. 313. ? Santa Barbara and shores of 



Pablo Bay. 



Dosinia lu7u/ula, Conr., p. 315. Monterey. 



Dosmia alfa, Conr., p. .315. Monterey. 



Peefen Pabloensis, Conr. San Pablo Bsy. 



Pallium Estrellanum, Conr., p. 313. E.strella Valley. 



Jaiiira bella, Conr., p. 312. Santa Barbara. 



7 1.. 



rj'^ > Ostrea Titan, Conr., Phil. Proc. 1855. San Luis Obispo. 



Pandora bilirafa, Conr., p. 267. [Closely resembles Komerlia 



bicarinata.~\ Santa Barbara. 

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



Santa Barbara. 

 „ ff 23. Diadora crneibidiformis, Conr., 1855, p. 267. \? = Puncturella 



cucullata, Gld.] Santa Barbara. 



Fossils of Gatun, Isthmus of Darien. 



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



„ „ 19. Tnrritella altilira, Conr. Gatun. 



„ „ 20. Turritella Gatunensis, Conr. Gatun, 



„ „ 20. Tritmi, sp. ind. Gatun. 



„ „ 21. ?Cytherea Dariena, Conr. [The figTire does not appear conspe- 



citic 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 fi'om Sta. Barbara, however, 

 are clearly of a veiy 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 rine/ens, 

 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 beiug such 

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

 it is fair to conclude that it had migrated from its head waters in the Pacif..c 

 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. AntiseU, 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 j)eriod ; and that duiing the whole of that 



80 



