a THE SAUROPOD DINOSAUR BAROSAURUS MARSH. 
A second species of Barosaurus, B. affinis, was named by Marsh as follows 1 : 
These Atlantosaurus beds, though overlooked by many geologists, have a great development around 
the margin of the Black Hills, especially along the southern and eastern borders. The bones of gigantic 
dinosaurs mark the outcrop of this horizon at various points. The one best known, the writer explored 
personally in 1889, near Piedmont, South Dakota, and there obtained remains of an enormous dinosaur, 
subsequently named Barosaurus. During the past season, important parts of the rest of the type skeleton 
were secured for the Yale Museum, by G. R. Wieland of that University. With these fossils were found 
remains of a much smaller species, which may be called Barosaurus affinis. 
As this paper was published the month of Professor Marsh's death, there was left 
to him no further opportunity for the elaboration of the description of either species, 
and that task has devolved upon his successors. 
Locality and Horizon 
The type specimens of Barosaurus were found in the eastern portion of the Black 
Hills, one and one-half miles east of Piedmont. The first specimen was discovered by 
Mrs. E. R. Ellerman, postmistress of Pottsville, on the land of Mrs. Rachel Hatch, a 
few rods southwest of the house. Thither Professor Marsh went, and, aided by Mr. 
J. B. Hatcher, secured the portion of the skeleton upon which he based the description 
published in 1890. In 1898, Professor Marsh directed G. R. Wieland to collect the 
remainder of the skeleton. This was done, and a large amount of material secured, 
including the remains of the smaller animal and a single carnivore tooth found in direct 
association with the larger specimen. Certain portions of the skeleton had, however, 
been removed as relics by the curious during the interim, but some of these were 
recovered by Doctor Wieland. 
The formation is Morrison, which is exposed in a narrow outcropping flanking the 
uplift of the Black Hills. East of Piedmont the thickness is 220 feet, 2 rapidly decreasing 
to 70 feet in a nearby locality, while near Rapid it is 165 feet in thickness. Mook says 
further : 
The name "Beulah shales" has been applied to the Morrison of the Black Hills region. The 
formation consists of the usual series of clays and shales, with thinner layers of sandstone and 
calcareous nodules. The prevailing color is gray, but other colors, such as red, maroon, pink, and 
purple, sometimes occur. Carbonaceous matter is sometimes present in the upper members. 
In a letter to Professor Marsh, dated Piedmont, September 12, 1898, Wieland 
writes : 
The skeleton runs through four vertical feet and the character of the clay changes frequently. 
Very little of the beautiful blue bone you showed me has been found. It is mostly black. 
A diagram of the quarry as drawn by Wieland is here appended (Fig. 2). 
Matrix and Inferred Habitat 
A sample of the matrix was referred to my late colleague, Professor BarrelL who 
reported as follows : 
1 Footprints of Jurassic Dinosaurs. Amer. Jour. Sci., 3d ser., Vol. 7, 1899, p. 228. 
2 C. C. Mook. A Study of the Morrison Formation. Ann. New York Acad. Sci., Vol. 27, 1916, p. 100. 
