had in view, in thus profusely beautifying creatures occupying so low a place in the scale of creation. European naturalists have hitherto fallen into the strangest absurdities concerning the motion of the bivalved shells, which five minutes' observation of nature would have served them to correct. Thus, they describe the upper part of the shell as the _lower_, and the _hind_ part as the front, and speak of them as moving along on their rounded convex surface, like a boat on its keel, instead of advancing with the edges or open part of the shell towards the earth. All these mistakes have been corrected, and the true mode of progression indicated from actual observation, by our fellow-citizen, Isaac Lea, whose recently published communications to the American Philosophical Society reflect the highest credit upon their author, who is a naturalist in the best sense of the term. As I wandered slowly along the borders of the run, towards a little wood, my attention was caught by a considerable collection of shells lying near an old stump. Many of these appeared to have been recently emptied of their contents, and others seemed to have long remained exposed to the weather. On most of them, at the thinnest part of the edge, a peculiar kind of fracture was obvious, and this seemed to be the work of an animal. A closer examination of the locality showed the footsteps of a quadruped, which I readily believed to be the muskrat, more especially as, upon examining the adjacent banks, numerous traces of burrows were discoverable. It is not a little singular that this animal, unlike all others of the larger gnawers, as the beaver, etc. appears to increase instead of diminishing with the increase of population. Whether it is that the dams and other works thrown up by men afford more favourable situations for their multiplication, or their favourite food is found in greater abundance, they certainly are quite as numerous now, if not more so, than when the country was first discovered, and are to be found at this time almost within the limits of the city. By the construction of their teeth, as well as all the parts of the body, they are closely allied to the rat kind; though in size, and some peculiarities of habit, they more closely approximate the beaver. They resemble the rat, especially, in not being exclusively herbivorous, as is shown by their feeding on the uniones or muscles above mentioned. To obtain this food requires no small exertion of their strength; and they accomplish it by introducing the claws of their fore-paws between the two edges of the shell, and tearing it open by main force. Whoever has tried to force open one of these shells, containing a living animal, may form an idea of the effort made by the muskrat: the strength of a strong man would be requisite to produce the same result in the same way.