  THE AMPHIBIA OF THE DEVONIAN AND MISSISSIPPIAN OF NORTH AMERICA. Evidences of the earliest land vertebrates are exceedingly scanty in the strata between the close of the Silurian and the opening of the Coal Measures, being represented solely by footprints. In the Devonian our knowledge of the group is confined to a single footprint, and in the Mississippian to series of footprints from several localities. These have been described by Lea (371), Rogers (Geology of Pennsylvania, pt. II, 1856, p. 831), Barrell (21), Dawson (223), and Branson (50). The last-named author has described a new species from the Mississippian of Giles County, Virginia. His description of the footprints, with a photograph of one of the series, are published herewith (plate 18, fig. 3). Branson (50) has given a rÉsumÉ of the knowledge of Mississippian Amphibia in North America. Thinopus antiquus Marsh, 1896. Marsh, Am. Jour. Science, II, p. 374, Nov. 1896, with figure. Type: Specimen No. 784, Yale University Museum. Horizon: Near top of Chemung, in the upper Devonian. [The] "specimen shows one vertebrate footprint in fair preservation, and with it part of another of the same series. These impressions are of much interest, both on account of their geological age and the size and character of the footprints themselves. The one best preserved [fig. 12] is nearly 4 inches in length, 2.25 inches in width, and was apparently made by the left hind foot. On the inner side in front of the heel, a portion of the margin is split off, and this may have contained the imprint of another toe. The other footprint was a short distance in front, but only the posterior portion is now preserved in the present specimen. It is probably the imprint of the forefoot. "The specimen [plate 18, fig. 4] ... was ... found in the town of Pleasant, one mile south of the Allegheny River, Warren County, Pennsylvania, by Dr Charles E. Beecher, who presented it to Yale Museum, where it still remains. "The geological horizon is near the top of the Chemung in the upper Devonian. In the same beds are ripple marks, mud cracks, and impressions of rain drops, indicating shallow water and shore deposits. Land plants are found in the same general horizon. Marine molluscs also occur, and one characteristic form (Nuculana) is preserved in the footprint slab" (Marsh). Fig. 12. Copy of Marsh's drawing of footprint of Thinopus antiquus, from the Devonian of Pennsylvania. × 1/3. This still remains after nearly 20 years the only evidence of air-breathing vertebrates in the Devonian of the world. Dromopus aduncus Branson. Branson, Jour. Geol., XVIII, No. 4, pp. 356-358, fig. 1, 1910. Type and other specimens in Oberlin College Museum. Horizon and type locality: Near the bottom of the Hinton formation in Giles County, Virginia. (Plate 18, fig. 3.) The following description of the shales and footprints are from Dr. Branson's paper cited above: "The Hinton shales, like the Mauch Chunk, seem to have been subaerial in origin and are made up for the most part of variegated shales interbedded with thin layers of argillaceous, fine-grained sandstone. The footprints occur in fine-grained sandstone, and remains of land plants are not uncommon in the same beds. "Twenty-two footprints made by one animal walking in a straight course were collected in a slab. They give the impression of having been made by a bipedal animal for part of the distance, but after the fourth print of the right foot impressions of the forefeet appear. The hindfeet had 5 digits, the middle digit being longest and the 2 inside of it being only slightly shorter and lying close together. Their outer ends were slender and flexible and usually curved inward toward the middle toe. The 2 outer digits formed wide angles with the middle one and were shorter than the inner ones. The second toe was webbed to within 8 mm. of the tip, the third toe to within 23 mm. of the tip. The impression of the web is well preserved in only one impression of the hindfoot. "The forefeet had 4 digits. The 3 inner digits were subequal in length, the 2 inner being more flexible and incurved near the ends. The outer digit is two-thirds as long as the second. The webbing extends about half the length of the digits. The heel impression is broader than that of the hindfoot.
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