Zoology of the Voyage of the Beagle. 291 



Monte Hermoso, and does not contain calcareous concretions. I found in 

 it a very few fragments of shells, and part of the remains of one quadruped. 



" From the bones in one of the skeletons, and likewise from those in part 

 of another, being embedded in their proper relative positions, the carcasses 

 of the animals, when they perished, were probably drifted to this spot in an 

 entire state. The gravel, from its stratification and general appearance, 

 exactly resembles that which is every day accumulating in banks, where 

 either tides or currents meet ; and the embedded shells are of littoral spe- 

 cies. But from the skeleton, in one instance, being in a position nearly 

 undisturbed, and from the abundance of Serpulce and encrusting corallines 

 adhering to some of the bones, the water, at the time of their burial, must 

 have been deeper than at present." Page 7. 



" Of these shells it is almost certain that twelve species, (and the coral- 

 line), are absolutely identical with existing species ; and that four more are 

 perhaps so ; the doubt partly arising from the imperfect condition of the 

 specimens. Of the seven remaining ones, four are minute, and one extreme- 

 ly imperfect. If I had not made a collection, far from perfect, of the shells 

 now inhabiting Bahia Blanca, Mr. Sowerby would not have known as liv- 

 ing kinds, five out of the twelve fossils : therefore, it is probable, if more at- 

 tention had been paid to collecting the small living species, some of the se- 

 ven unknown ones would also have been found in that state. The twelve 

 first shells, as well as the four doubtful ones, are not only existing species, 

 but nearly all of them inhabit this same bay, on the shores of which they 

 are likewise found fossil. Moreover, at the time, I particularly noticed 

 that the proportional numbers appeared closely similar between the diffe- 

 rent kinds, — in those now cast up on the beach, and in those embedded with 

 the fossil bones. Under these circumstances, I think, we are justified, (al- 

 though some of the shells are at present unknown to conchologists,) in con- 

 sidering the shingle strata at Punta Alta, as belonging to an extremely 

 modern epoch." Page 9. 



The most important consideration which occurs to us as 

 arising out of the facts noticed by Mr. Darwin in his exami- 

 nation of the deposits of the Pampas and neighbouring loca- 

 lities, is that the series of embedded fossil Mammalia should 

 consist of extinct genera or species, including some forms 

 with very remote affinities to any existing at the present day; 

 whilst the marine shells which so frequently accompanied the 

 bones of quadrupeds, were, with two or three exceptions, re- 

 ferrible to species inhabiting the nearest seas. 



Mr. Lyell, it is true, has endeavoured to shew that in the 

 class Mammalia species have not an existence throughout so 

 extended a period of time as in the Mollusca; but in the pre- 

 sent instance, we apprehend that the revolution which has 

 taken place in the South American quadrupeds, has occurred 

 within so recent period, that a solution of the phenomenon 

 will hardly be discovered in the slow and gradual operation 

 of existing causes. Were it not for the circumstance of seve- 

 ral skeletons having been discovered, with the different bones 

 in their relative positions, we should have ventured to remind 

 Mr. Darwin that the fossils of two or more geological periods 

 may be introduced, to an unlimited extent, into one and the 



