Ch. XII.] ORGANIC REMAINS OF SUBAPENNINES. 163 



these pushed their deltas farther out, they threw down the 

 sand upon part of the bed of the sea already occupied by finer 

 and more transportable mud. 



Organic Remains. I have been informed, by experienced 

 collectors of the Subapennine fossils, that they invariably pro- 

 cure the greatest number in those winters when the rains are 

 most abundant, an annual crop, as it were, being washed out of 

 the soil to replace those which the action of moisture, frost, 

 and the rays of the sun, soon reduce to dust upon the surface. 



The shells in general are soft when first taken from the marl, 

 but they become hard when dried. The superficial enamel 

 is often well preserved, and many shells retain their pearly 

 lustre, and even part of their external colour, and the ligament 

 which unites the valves. No shells are more usually perfect 

 than the microscopic, which abound near Sienna, where more 

 than a thousand full-grown individuals are sometimes poured 

 out of the interior of a single univalve of moderate dimensions. 

 In some large tracts of yellow sand it is impossible to detect a 

 single fossil, while in other places they occur in profusion. 



The Subapennine testacea are referrible to species and fami- 

 lies of which the habits are extremely diversified, some living 

 in deep, others in shallow water, some in rivers or at their 

 mouths. I have seen a specimen of a fresh-water univalve 

 (Limnea palustris), taken from the blue marl near Parma, full 

 of small marine shells. It may have been floated down by the 

 same causes which carried wood and leaves into the ancient sea. 



Blocks of Apennine limestone are found in this formation 

 drilled by lithodomous shells. The remains not only of tes- 

 tacea and corals, but of fishes and crabs, are met with, as also 

 those of cetacea, and even of terrestrial quadrupeds. 



A considerable list of mammiferous species has been given 

 by Brocchi and some other writers ; and, although several 

 mistakes have been made, and the bones of cetacea have some- 

 times been confounded with those of land animals, it is still 

 indubitable that the latter were carried down into the sea when 

 the Subapennine sand and marl were accumulated. The same 



M 2 



