Contrast this with the diminutive _Laosaurus_, a 2½-foot biped which ranks as the smallest dinosaur yet taken from the deposit. This tiny creature had hollow limb bones and was one of the agile, quick-running types. Only one was found. When discovered, Douglass thought it a “baby” dinosaur, but study proved it to be a full-grown specimen. The condition of the skeleton reflected considerable agitation before and after burial. It lay on its back, the limbs distended. The tail was gone and the skull crushed. In many respects, the most interesting dinosaur found was the sauropod, _Barosaurus_. It was an extremely long-necked form, some of the individual cervical vertebrae measuring 3 feet in length. Two specimens were excavated. The flesh-eaters, as might be expected from their scarcity in other localities, made but a small showing. Two specimens of _Antrodemus_ were unearthed. Thirty feet long, this animal was the ranking predator of its day, although hardly comparable to the towering _Tyrannosaurus_ that entered upon the earthly scene at a later age. _Stegosaurus_ remains—so abundant that Douglass grew tired of them—added a bizarre note. An armored form, it was equipped with a frill of bony plates that extended the length of the back and terminated in a pair of sharp spines. Its chief claim to fame rests in its supposed two sets of “brains,” one a motor-control center situated in the hip region, and the other in the usual place. Everywhere they dug, the excavators found fresh material—a vast jumble of bones so concentrated and intermingled as to make it difficult to distinguish one specimen from another. Douglass was amazed. Obviously, it was not with animals of a single area that he was dealing, but of an entire region. He was dealing with a dinosaur _fauna_. He was also perplexed. How did so many different types happen to occur in one small locality? Slowly, as Douglass’s acquaintance with the deposit grew, the answer came. It was, he reasoned, the work of a river. The sandstones were ancient sediments. In their structure and composition lay the story of swift swirling currents. The coarse granular texture told of fast water; the crossbedding, of shifting channels; the grouping of the bones into clusters, of eddies. It all added up to an old delta deposit at the mouth of a river, a region of bars where the carcasses of dinosaurs brought down stream accumulated. Settling, the great hulks became buried as they sank into the receptive sand. A number of carcasses multiplied ... and slowly, as flesh and ligament decayed, the bones became mingled, eventually to petrify and remain preserved through the ages. WORK METHODS