594 REPORT—18638. 
Page. Plate. Fig. : 
70. Il 4. Mya Montereyana, Conr., p. 313. [Figure resembles Periploma 
argentaria.| Monterey Co. 
? Mya subsinuata, Cour. | Comp. Macoma inquinata. | Monterey Co. , 
Arcopagia medialis, Conr., p. 814. Like A. biplicata, Conr., of 
the Maryland Miocene. (Closely resembles Lutricola alta, Conr. | 
Monterey Co. 
7. Tapes linteatum, Conr., p. 314. California. 
8. Arca canalis, Conr., p. 314. Santa Barbara. 
9. Arca trilineata, Conr., p. 314. Santa Barbara. 
43 55 10. Arca congesta, Conr., p. 314. California. 
Il. ig bs 
s 
Sor 
71. . Axinea Barbarensis, Conr. [Closely resembles Pect. intermedius. | 
55 5 . Mulinia densata, Conr., p. 313. ? Santa Barbara and shores of 
Pablo Bay. 
5 Dosinia longula, Conr., p.315. Monterey. 
13. Dosinia alta, Oonr., p.315. Monterey. 
14, Pecten Pabloensis, Conr. San Pablo Bay. 
15. Pallium Estrellanum, Cony., p.313. Estrella Valley. 
16. Janira bella, Cony., p.312. Santa Barbara. 
ie } Ostrea Titan, Conr., Phil. Proc. 1855. San Luis Obispo. 
25. Pandora bilirata, Conr., p. 267. [Closely resembles Kennerlia 
bicarinata.| Santa Barbara. 
9 » 24. Cardita occidentalis, Conr., 1855, p. 267. [P= C. ventricosa, Gld.] 
Santa Barbara. 
is 3 23. Diadora crucibuliformis, Conr., 1855, p. 267. [? = Puncturella 
cucullata, Gld.] Santa Barbara. 
Fossils of Gatun, Isthmus of Darien. 
72. VV. 22. Malea ringens, Swains. Gatun. 
4 » 19. Turritella altilira, Cony. Gatun. 
ee » 20. Turritella Gatunensis, Conr. Gatun. 
py » 20. Triton, sp. ind. Gatun. 
or » 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 tothe 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 
