Cacœcia rosana Linn. Full-grown Larva.-Dull whitish green. half of the second segment dull black. Head and posterior There are also two blackish spots on the sides of the second segment. The feet are pitchy black, and the abdominal legs the same color as the body. Length, 13 mm. Cacœcia parallela Robs. Full-grow Larva.-Dull olive green. Head dull orange; second segment paler yellow, with two black dots in front on a narrow white line, and a black semi-circular band passing along the base of the segment and ending at the exterior margin. The remaining segments have each eight white tubercular spots from which spring whitish hairs. Feet blackish. Abdominal legs concolorous with the body. Food-plants-Willow, Aster. Length, 20 mm. Article XI.-FOSSIL MAMMALS OF THE WAHSATCH AND WIND RIVER BEDS. COLLECTION OF 1891. By HENRY FAIRField Osborn and J. L. WORTMAN. With One Plate and Eighteen Figures in Text. INTRODUCTION. This paper is mainly given to a description of a collection made by Dr. Wortman in the Wahsatch (Big Horn) and lower Bridger (Wind River) beds during the summer of 1891. It includes the following special articles, each writer being responsible only for his own: I.-Homologies and Nomenclature of the Mammalian Molar Cusps (H. F. 0.)....... .p. 94 .p. 84 0.). p. 101 Horn .P. 135 VI.-Narrative of the Expedition of 1891 (J. L. W.).. .p. 144 Many new facts of great interest are brought out by the material in this collection, although Professor Cope has worked for years upon the Wahsatch fauna, with the assistance of Dr. Wortman in the field. 1. The lower jaw of Anaptomorphus homunculus is found to contain three premolars, instead of two, as in the type species A. amulus (p. 102). 2. The genus Palæonictis, hitherto found only in the Suessonian of France is also found in the American Wahsatch. The complete dentition and the facial region of the skull show that it is an extremely modified type, with only a single fully functional upper molar. It represents a family, the Palæonictidæ, including Ambloctonus (p. 106), and perhaps Patriofelis (p. 97), and is more like the Cats than any Creodont which has yet been found (pp. 95, 103). [September, 1892.] [81] 6 3. Additional remains of Oxyana show that the manus of this Creodont had a separate scapho-lunar and an os-centrale; the lumbar vertebræ have involuted zygapophyses; the pes is not cleft as Cope has described it. The incisors were (p. 109). 4. Among the Mesonychidæ is a small new form related to Dissacus of the Puerco, and a very large new species of Pachyana, by far the largest Creodont which has yet been found in the Wahsatch (p. 112). 5. The genus Anacodon, which has been doubtfully placed by Cope among the Condylarthra, is found to belong to the group of Creodonts with tubercular molars near Arctocyon. The upper and lower molar cusps are obtuse and covered with a great number of accessory tubercles; the premolars are reduced in number and pointed (p. 115). 6. Complete limbs of Coryphodon show that the fore foot was digitigrade, as in the Elephant, while the hind foot was fully plantigrade, the whole plantar surface resting upon the ground as in the most primitive Ungulates (pp. 120-122). 7. The complete dentition of Systemodon, the earliest form of Tapir, is described (p. 124). 8. The complete limbs of Heptodon (Wind River), show that this animal belongs, with Helaletes of the Bridger, to a side line of small Perissodactyls with greatly reduced lateral toes. This family of Helaletidæ extended from the lower Eocene into the Miocene; it is not ancestral to the Tapirs as Marsh supposed, nor is it (Heptodon) ancestral to the Hyrachyus series as Cope has suggested. The tooth structure is intermediate between the two. The foot structure is highly modified and aberrant both in the marked shortening of the lateral digits and in the long narrow terminal phalanges. Heptodon calciculus was a small, light limbed animal, somewhat of the dimensions of the Peccary (p. 129). 9. Many additional characters of Palæosyops borealis, the earliest known representative of this important Bridger genus, are noted (p. 132). We pass by a large number of forms in the collection in which there is nothing to be added to the observations of Cope. In the field great care was taken to observe and record the localities, and especially to note whether the fossils were from the lower, middle, or upper portions of the great Wahsatch beds of the Big Horn Basin, which are variously estimated at 2000 to 3000 feet in thickness. Of course this depth of rock represents a very long period of time in which the various species underwent considerable modification. We have therefore published in full Dr. Wortman's field notes upon the geology of the Big Horn and Wind River Basins, as well as geographical details, which will be of great service to collectors in the future (pp. 135-144). We give (p. 83) a preliminary conspectus of the distribution of the species; this cannot be fully made out until all the species are determined by a comparison with Cope's types. Before taking up the systematic description of the collection, we offer three introductory sections, treating of the structure of the molar teeth, the classification of the Perissodactyla, and the origin of the Felidæ. I. HOMOLOGIES AND NOMENCLATURE OF THE MAMMALIAN MOLAR CUSPS. In October, 1888, a table of nomenclature for the cusps of the molar teeth of mammalia was published in the 'American Naturalist," The terms were carefully chosen with reference to the gradual rise of these cusps from the single cone of the reptilian type, through the tritubercular to the sexitubercular stages." They have since been wholly or in part adopted by Cope, Scott, Lydekker, Schlosser, Flower, and lately by Rütimeyer. The tritubercular stem form has been recognized by Döderlein and Fleischmann, but these authors have employed various Greek symbols for the cusps. The latter has opposed the adoption of similar terms for the main cusps of the upper and lower molars, upon the ground that Cope and myself have mistaken the homolo 3 1 Osborn, The Nomenclature of the Mammalian Molar Cusps, op. cit., p. 927. 2 See also Evolution of Mammalian Molars to and from the Tritubercular Type, Am. Nat., December, 1888. a Schlosser, Die Differenzierung des Säugethiergebisses, Biologisches Centralblatt, Juni, 1890. 4 Die Eocäne Säugethier-Welt von Egerkingen, Zurich, 1891. |