species of squoloid selachians, or cestratront, and three genera of teliosts. Molluscan remains are rare.
Extensive beds of peat exist in Northern Middle Iowa, which, it is estimated, contain the following areas in acres: Cerro Gordo, 1,500; Worth, 2,000; Winnebago, 2,000; Hancock, 1,500; Wright, 500; Kossuth, 700; Dickinson, 80.
Several other counties contain peat beds, but the character of the peat is inferior to that in the northern part of the State. The character of the peat named is equal to that of Ireland. The beds are of an average depth of four feet. It is estimated that each acre of these beds will furnish 250 tons of dry fuel for each foot in depth.
The only deposits of the sulphates of the alkaline earths of any economic value in Iowa are those of gypsum at and in the vicinity of Fort Dodge, in Webster County. All others are small and unimportant. The deposit occupies a nearly central position in Webster County, the Des Moines River running nearly centrally through it, along the valley sides of which the gypsum is seen in the form of ordinary rock cliff and ledges, and also occurring abundantly in similar positions along both sides of the valleys of the similar streams and of the numerous ravines coming into the river valley.
Besides the great gypsum deposit of Fort Dodge, sulphate of lime in the various forms of fibrous gypsum, selenite, and small, amorphous masses, has also been discovered in various formations in different parts of the State, including the coal-measure shales near Fort Dodge, where it exists in small quantities, quite independently of the great gypsum deposit there. The quantity of gypsum in these minor deposits is always too small to be of any practical value, and frequently minute.
Sulphate of strontia (celestine) has only been found in Iowa, so far as is known in one place-Fort Dodge. It occurs there in very small quantity in both the shales of the lower coal measures and in the clay that overlies the gypsum deposit, and which are regarded as of the same age with it. The first is just below the city, and occurs as a layer intercalated among the coal measure shales, amounting in quantity to only a few hundred pounds' weight. The mineral is fibrous and crystalline, the fibers being perpendicular to the plane of the layer. Breaking also with more or less distinct horizontal planes of cleavage, it resembles, in physical character, the layer of fibro-crystalline gypsum before mentioned. Its color is light blue, is transparent and shows crystalline facets upon both the upper and under surfaces.
Sulphate of baryta (barytes, heavy spar) has been found only in minute quantities in Iowa. It has been detected in the coal-measure shales of Decatur, Madison and Marion Counties, the Devonian limestone of Johnson and Bremer Counties and in the lead caves of Dubuque. In all these cases, it is in the form of crystals or small crystalline masses.
Sulphate of magnesia (epsomite) having been discovered near Burlington, there are represented in Iowa all the sulphates of the alkaline earths of natural origin, except the sulphate of lime, which occurs in very small quantity. Even if the sulphate of magnesia were produced in nature, in large quantities, it is so very soluble that it can accumulate only in such positions as afford it complete shelter from the rain or running water. The epsomite was found beneath an overhanging cliff of Burlington limestone.. It occurs in the form of efflorescent encrustations upon the surface of stones and in similar small fragile masses among the fine debris that has fallen down beneath the overhanging cliff.