Proceedings of the Boston Society of Natural History, Band 22

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Boston Society of Natural History., 1884
 

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Seite 442 - Rau,79 who first described them, that " if the shape of the described implements (shovels and hoes) did not indicate their original use, the peculiar traces of wear which they exhibit would furnish almost conclusive evidence of the manner in which they have been employed ; for that part with which the digging was done appears, notwithstanding the hardness of the material, perfectly smooth, as if glazed, and slightly striated in the direction in which the implement penetrated the ground.
Seite 7 - The purpose of this laboratory is to afford opportunities for the study and observation of the development, anatomy, and habits of common types of marine animals, under suitable direction and advice.
Seite 178 - Practically, when a naturalist can unite two forms together by others having intermediate characters, he treats the one as a variety of the other, ranking the most common, but sometimes the one first described, as the species, and the other as the variety.
Seite 9 - The great need of an institution for teaching field work cannot be properly estimated by the number of those who are attracted by the opening of such opportunities for study. The mental condition of those who attend, and what it has done for them, and the sphere of influence which it reaches through them, are the only true standards by which its present and future usefulness can be properly measured. Nearly all the pupils were persons who could be termed 'well educated...
Seite 129 - ... the larger rivers, such as the Toar and Molasses in the vicinity of Baracoa, the reef in question was completely interrupted, and these streams discharge into broad, open bays ; while the lower portions of their valleys show, equally with the harbors, that the land is sinking. They are half-drowned valleys, filled to a considerable depth with land detritus, conditions which could not exist if the land were rising or had recently risen. But the most satisfactory evidence that the ancient reefs...
Seite 43 - Ice, or glaciers, by their immense expanding powers, must beyond doubt have produced this change in their original form, from this circumstance, that they were continually sliding downwards from the higher mountains to the lower districts and, by this progressive motion, carried with them the masses of stone which they had torn from the mountains.
Seite 129 - ... present level, each river scoured out a large part of the sand and gravel which it had deposited, and cut a narrow channel through the reef itself. During this period of elevation, Cuba, like most rapidly rising lands, had few harbors; but when subsidence began, the sea occupied the channels and basins which had been excavated and cleared out by the rivers, and thus a large number of harbors came into existence. Opposite the mouths of the larger rivers, such as the Toar and Molasses in the vicinity...
Seite 479 - ... resting, presumably, upon a volcanic foundation. The oceanic islands are, of course, merely the tops of submerged mountains ; and it is only with the highest points of the continents that they can be properly compared. Now, supposing the existing continents were submerged to an average depth of 15,000 feet, what would be the geological character of the land remaining above the sea? Palaeozoic and Mesozoic rocks would probably be about as scarce in it as in modern oceanic islands. As a rule, the...
Seite 272 - Hercoglossa, as do also the broad lateral saddles of the later larval stages in some species. There are no annular lobes at any stage in the Triassic, according to Mojsisovics. They do not seem to be present in some of the Jurassic and Cretaceous species, at least during the early stages, and are very small in some adults. The Triassic species are nearly related to Grupoceras, according to Mojsisovics' figures and descriptions in
Seite 263 - ... ascending trunk of the straight and arcuate forms. The same is true of the Ammonoidea in the Silurian, but only one short series, the Nautilinidae, arises from the common trunk of straight cones. The close-coiled shells of this one family became the stock form for the whole of the Ammonoidea. The Nautiloidea of the Mesozoic are all nautilian forms, and their genetic series do not present the rapid changes of form observed in the Paleozoic ; they are all close coiled and have, as observed by M....

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