ADDENDA. 611 



are found in the southern hemisphere, and likewise of some mammaUa 

 and of birds. With respect to the parrot of the Strait of Magellan, Mac- 

 quarrie Island in lat. 55° S. and long 160° E. offers an analogous instance, 

 in possessing a species of this genus. I am, however, now enabled to 

 bring forward a more important observation, as directly bearing on the 

 evidence by which geologists have chiefly judged of the climate of ancient 

 Europe, namely, on the character of the marine productions of the south- 

 ern hemisphere. In my journal I have remarked that the southern seas 

 teem with life, under innumerable forms ; and the truth of this remark is 

 amply attested by the vast herds of great unwieldy seals with which the 

 shores of Patagonia, the Falkland and the Antarctic islands, were, ac- 

 cording to the narratives of all the early navigators, almost covered. 

 Having mentioned these facts to Mr. George B. Sowerby, he informs me, 

 that the shells of the southern part of the southern hemisphere have some 

 affinity in general character with those of the intertropical seas, or rather 

 that they are of much larger size and of more vigorous growth than the 

 analogous species (excepting the chitons of California) under correspond- 

 ing zones in the northern hemisphere. Thus the immense size of the 

 Patellae, Fissurellae, Chitons, and Barnacles of the Strait of Magellan, and 

 the large size of the former at the Cape of Good Hope, may be taken as 

 instances. On the east coast of South America (in lat. 39°) three species 

 of Oliva (one of large size), a Voluta (and perhaps a second species), 

 and a Terebra, are amongst the most abundant shells on the mud-banks of 

 Bahia Blanca. Another species of Voluta is found as far south as 45°, 

 and there is some reason to believe, even much further. Oliva, Voluta, 

 and Terebra are amongst the best-characterized tropical forms, that is, 

 both the individuals and species of these genera are extremely abundant 

 in the intertropical seas, whilst they are very rare, or do not exist, on the 

 shores of temperate countries. It is doubtful even if one small species of 

 these three genera, an Oliva, inhabits the southern shores of Europe ; 

 ■whilst in a higher latitude, on the coast of South America, species of all 

 three are the most abundant kinds. 



At Bahia Blanca many of these shells are embedded in gravel, and have 

 been raised above the level of the sea. Now let us suppose that the 

 climate of South America and of the surrounding seas were to undergo 

 some change, so as to become in every respect like that of Europe ; it 

 can, I think, scarcely be doubted, that the shells of the abovementioned 

 genera would gradually become extinct, and be replaced by others better 

 adapted to the new climate. What, then, would a geologist say, who 

 entertained the generally-received opinions on the distribution of organic 

 beings in accordance with our knowledge of the northern hemisphere (or, 

 rather, in this imaginary case of both hemispheres), when he found 

 these gravel beds abounding with Olivas, Volutns, and Terebras? — such 



2 g 2 * 



