400 DE. GtJNTHEE 0^ THE FISHES OF CENTEAL AMEEICA. 



geology will furnish us with the proof of the former partial submergence of a part of 

 Central America, as it has done with respect to the northern part of Scandinavia. We 

 should then be able to speak with more confidence of the permanence, or rather endu- 

 rance, of the characters of a specific type, and arrive at a somewhat more definite idea 

 of the age of species which must have existed before those geological changes were 

 completed '. 



Sir Charles Lyell has directed my attention to collateral evidence from other classes 

 of the animal kingdom, by which the partial identity of the faunas of the two coasts is 

 shown, although not in an equally conclusive manner. The majority of malacologists 

 appear to have presumed a j^iiori their distinctness, and consequently described Pacific 

 shells generally as distinct from Atlantic species. However, Dr. Morch, in a paper in 

 which he describes or enumerates about 360 Panama species, makes the following 

 remarks (Pfeifi". Malakozool. Blatt. 1859, p. 107):— 



" The tropical [molluscan] faunse may be classed in two principal divisions, the Indian 

 and the Atlantic. To the latter belong, 1, the Guinean (Senegalian) ; 2, the Antillian ; 

 and 3, the Panaman, which, although belonging to the Pacific, appears to be most 

 analogous to the Guinean. A great number of species, especially of Bivalves, have 

 been regarded as identical with those from the eastern (Brazilian) shore. I believe I 

 can prove that they are difi'erent. Certain irregular mollusks cannot be separated 

 diagnostically ; but I can recognize them by their general habit. It is at all events a 

 fact that no species stamped with definite characters (wohlausgepragt) is identical on 

 both sides of the isthmus. The Panama species may be divided into: — 1, those 

 analogous to West-Indian ; 2, those analogous to species from Guinea and Senegal ; 

 ;-), those very remotely analogous to East-Indian species." 



' I may on this occasion recur to a remark made by me in Proc. Zool. Soc. 1858, p. 381, witli regard to the 

 sea-snakes obsei-ved in the Bay of Panama by M. Salle, Capt. Dow, and Mr. Salvin. There is now not the least 

 doubt that the snakes seen were Pehmi/s bicolor, and that they are, moreover, very common there. I find' that 

 Dr. Seemaun (Voy. ' Herald,' i. p. 205) abeady mentions them. But I am much inclined to think that this 

 most common Indian species has migrated eastwards, and that its arrival on the West- American coast is of 

 veiy recent date. Dampier and the other bucaniers who have left us records of their adventures, and who 

 passed weeks and months in the Bay of Panama, could not have failed to observe them, and to mention them 

 in their notes, just as they did on other occasions. It is also probable that these snakes would have spread 

 into the Atlantic Ocean, had they been so numerous on the Pacific side at the time when a communication 

 existed between the two oceans. 



Whilst this paper was passing through the press, I found two notices of the existence of water-snakes 

 on the western coasts of South America, in seas considerably more southwards than the Bay of Panama. The 

 notes are in Capt. Sharp's Voyage in " The History of the Bucaniers of America." London, 1699, 8vo, vol. ii. 

 p. 50 : " As we sailed " [near Cape St. Francisco, which is nearly under the equator] " we saw multitiides of 

 Grampusses every day ; as also Water-snales of divers colours."' And p. 72, when sailing in lat. 19° S., the 

 author mentions " A huge shoal of fish, two or three Wafer-snakes, and several Seah." I find in another part 

 of the same work a note which I believe to be the first description of Tapinis bairdi. The part has a separate 

 title-page, "A Journal of a Voyage made into the South Sea by the Bucaniers or Freebooters of America from 

 the year 1684 to 1689. Written by the Sieur Eaveneau de Lussan." Lond. 1698, 8vo. The Indian name of 

 the Tapir is given as Alcmijwwye, page 16. 



