It9 . __ . . ' Jlnniiqcrlpt rtv,vlvivl ltv thc 13lllor l q W?. 191.7 189) MOON, 51'U'DY .OF T H E NORRISON FOIZ.lI.4TIOA'
41:data gathered for use in the above-nientioncd monograph. C'onCcrcncee ' have bccn held with' Professors A. I\'. Grabau, C. P."BerI& and 1). w. Johnson, of Columbia University, a.110 have made suggestions in regard to'the work. Messrs. W. T. Lee, N. H. Darton, W. Cross and C. T. h p t o n have added data regarding the distribution of the Morrison in the soutliern areas, and the director of the United States Geological Siirvey has' given. permission to use these unpublished data, and to use the map which was redrawn by Survey draughtsmen from an original by the writer. Valuable information has also hcen gibcn by Mr. S. H. Knight, '44 Las Vegas. TIie main line of outclaps then swings northenstward to a point 15 miles or 60 southwest of Clayton. The outcrops along the inountnin front in Colorado and New Afesico occur in hog-backs; The north-, east-southwest line of surface occurrence in Rew Jlesico is an irregular clifi. Tlle lines of outcrops are not completely continuous. At Golden the Morrison has been crowded out by igneous action, and at Manitou and other places it has disappeared through faulting. Outcrops also occur in the cmyons of tile Purgatory, Bpishapa and other rivers in Colorado, and of the Cimarron in New Mexico and Oklahoma. ' A. R. Marvine (1574, 3 ) , in the seventh Annual Report of the U. S. Geological and ' Geographical Survey of the Territories, describes the "Jiirasaic" or the beds overlying the red scrics of supposed 'Yrinssic age, as follows:"General clLaraciers,--'rhc series of strata lying licit above the red beds form a group of rocks in wliich the thin-bedded and shaly'element 'decidedly predoni'inntcs. The outcropping edges of 'these beds have therefore generally been inore eroded away than the harder beds above and l)elow, so that thcy generally i1l)Pciir in valleys ; and being soil covered, t h y are not usually well esposcd. "The arenaccous clement still predominntcs, though argillaceous mnteri;il is often prcscnt to n very Inrge cxtcilt, while bcds of iinpiirc linicstone ~(~i i r -o n e 01 wliicli q~pcars very persistent--and gypsiini is ficqncnt in thin layers, and somctiincs occurs in worlzablc quailtitics a i d of good 'quality. As beforc, red is the prcwiling color, though a scrics of lllilrlted vilricgatC(1 shales occiir, 'nird wcntIioring frii,ucntlg' pro(1uccs an asliengrtiy tint upon the surlacc. . . ." So~iic of tlicsc 1)ctls arc prohaldy o f lo\wi* liorizon than tlic true Morri-Tlic following tlcscription oC tlic 31!)rrixun loriniition cast nf tlic .I
In the study of the sauropod dinosaurs which has been carried on by the writer for a number of years under the direction of Professor H. F. Osborn in connection with the preparation of the latter's monograph on these reptiles, some problems have presented themselves upon which a study of the habitat, or immediate environment, has a bearing. The course, or trend, of evolution in a group of organisms is limited, or controlled, by two things: (i) the heritage or assemblage of characters inherited from the ancestors; and (2) the environment. The environment offers the organism opportunities for developing along a limited number of lines. What these lines will be depends upon the general character of the environment. For instance, upon inland plains advanced aquatic adaptations, such as are characteristic of marine organisms, will be barred out, and under strictly marine conditions the development of cursorial locomotor apparatus is impossible. This is true no matter what may be the heritage of the organism under discussion. Within certain limits, however, the environment offers the possibilities or opportunities for evolution along a number of lines. The heritage furnishes the material or instruments by which, or by a modification of which, the organism may evolve along one or more of these lines. In working out adaptations and habits in a group of animals such as the Sauropoda, morphology, together with comparison with living forms, will be the most important guide. Morphological structures have meanings, and if these meanings can be interpreted the habits of the animals possessing the given structures can be determined to a certain extent. A study of the environment of 459
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