[101] In rain water puddles, we remarked a new species of Branchiopode belonging to the genus Apus; small crustaceous animals, which exhibit a miniature resemblance to the King or Horse-shoe Crab, (Himulus polyphemus,) of our sea coast, but which are furnished with about sixty pairs of feet, and swim upon their back. The basins of water, which contained them, had been very much diminished by evaporation and infiltration, and were now crowded to excess, principally with the apus, great numbers of which were dying upon the surrounding mud, whence the water had receded. This species is distinguished from the _productus_ of Bosc, and _montagui_ of Leach, by not having the dorsal carina prolonged in a point behind; and from _cancriformis_, by the greater proportional width of the thorax, and more obtuse emargination behind. The length of the thorax along the middle, is three-tenths of an inch, and its greatest breadth somewhat more. It may be named _Apus obtusus_. A very large species of Cypris, also inhabits these small rainwater pools in great numbers, of which the valves are more than one-fifth of an inch in length.—JAMES. Being now at a place where, as our guide informed us, the Pawnees often cross the Platte, and as it was our intention to ascend on the other side of the river, Major Long rode across to ascertain the practicability {150} of fording; but the summer freshet being now at its height, it was found the river could not be crossed without swimming, and the design was relinquished. Six of our party, including the hunters, were sent out in pursuit of game. At camp, observations were taken for ascertaining longitude and other purposes. At evening, Mr. Peale returned, having killed an antelope at the distance of ten miles from the camp, and brought it within about four, where being fatigued and hungry, he had made a fire, cooked and ate part of the animal, and left the remainder, suspending a handkerchief near it, to protect it from the wolves. Soon afterwards others returned, and when all were collected, it appeared there had been killed one bison, two antelopes, and a hare, all at a distance from camp. Horses were accordingly sent out to bring in the meat, a part of which we attempted to dry during the night, by cutting it in thin pieces and exposing it over a slow fire, but a storm of wind and rain, which continued greater part of the night, prevented our success in this attempt. 21st. The storm continued throughout the night, and the following day was cold, with a heavy mist from the south-east.