=Pearl Mussels.=--In his report to the United States Fish Commission on the Pearly Fresh-Water Mussels of the United States, Mr. Charles T. Simpson speaks of the great variety of conditions under which they live. They show great capacity for adaptation. Most of them are found in shallow water, but certain forms live at considerable depths. Some bury themselves among the fibrous roots of trees, some in the muddy, sandy banks just below the surface of the water, and some, as in Lake Tiberias (Palestine) and Lake Tanganyika (Africa), under six hundred or more feet of water. Ordinarily they die in a very short time if taken out of the water--in from twenty-four to forty-eight hours, as a rule--and they generally die in a few hours when exposed to the sun. But many species, thus tender in the open air, will lie buried in dried mud for a long time. In June, 1850, a living pond mussel was sent to London, from Australia, which had been out of water for more than a year. Along a small stream near Braidentown, Fla., which runs only during about three months in summer and is dry the rest of the year, thousands of a large colony of _Unio obesus_ may be found just buried in the sandy banks or among the flags and rushes of the bottom, where there is very little moisture, all in healthy condition. Mr. Simpson has laid these mussels in the sun for months without killing them. The specimens which live in perennial water seem to die soon if removed from it, while those which inhabit streams or ponds that often dry up will live a long time out of water. Some species in rocky streams live in the crevices of the rocks. In the Big Vermilion River, in La Salle County, Illinois, a swift, rocky stream, the author has found living mussels that had been so washed about that nearly all the epidermis was destroyed. The shells in such streams are usually heavier than those in more quiet water. MINOR PARAGRAPHS. Prof. Frederick Starr, of the University of Chicago, has made two excursions to Mexico for the purpose of establishing the physical types of the aborigines by means of measurements, photographs, and casts. He studied twelve tribes, half of which were almost unknown to science, and made measurements of more than eleven hundred and fifty men and three hundred women. On his last trip he rode one thousand miles among the mountains on horseback. In a recent paper in the Open Court he takes notice of frequent and curious survivals of pagan belief to be remarked among these peoples, although they are all supposed to be devout Christians. In one instance, which is specially described, an idol bearing some resemblance to those found among the ruins of the ancient cities occupied a station in the church by the side of the crucifix, sharing the honors with the statue of the Virgin on the other side. Grief and consternation prevailed among the Indians when the idol was taken away by the ecclesiastical authorities. * * * * *