. Bulletin of the Natural History Society of New Brunswick . ere denser, conditions which wouldfavor a more uniform distribution of heat over the earthssurface and enable the animals of the tropical seas to invadethe Arctic circle. While these early sea snails and straight nautiloid formshad been growing up and developing in the warm seas of theinterior, another type of beings had been fitting themselvesto the very different conditions of existence in the NorthAtlantic. These, the Graptolites, were roving creatures,fitted to propagate their kind in the open sea. Through thesubsequent ages we f
. Bulletin of the Natural History Society of New Brunswick . ere denser, conditions which wouldfavor a more uniform distribution of heat over the earthssurface and enable the animals of the tropical seas to invadethe Arctic circle. While these early sea snails and straight nautiloid formshad been growing up and developing in the warm seas of theinterior, another type of beings had been fitting themselvesto the very different conditions of existence in the NorthAtlantic. These, the Graptolites, were roving creatures,fitted to propagate their kind in the open sea. Through thesubsequent ages we find them gradually simplifying theirstructure, so that the colonies of many branches of the earliesttimes are reduced at last to colonies of one stem without abranch, and with rows of cells on one side of the stem modern times we have the Sertularians, branching coloniesof minute creatures as representatives of the Graptolites. In THE CLIMATE OF ACADIA IN THE EARLIEST TIMES. 13 Sketch Map showing the Distribution op Animals in LowerOrdovician 7 ^ • / Areas of Laurentian rocks as in the preceding map. Outcrops of the Chazy fauna, found chiefly in limestone rocks,and areas of sandstones supposed to be of that age. Corals andnumerous forms of molluscs appeared at this time, and the fauna issupposed to have flourished in shallow, warm seas. Outcrops of the Arenig fauna The rocks of this fauna are,to a large extent, mud rocks, with thin flagstones, and the fauna issupposed to indicate the prevalence of colder and deeper waters thanthose of the Chazy fauna. Since the above map was drawn I havelearned that the Arenig fauna has been recognized in the south ofFrance ; if this region were included in the Arenig area, the shadedportion of this map would correspond almost entirely with that ofthe map on page 11. Compare the range of the faunas represented on this sketch-map with those of the preceding. The upper Cambrian faunasare intermediate between the two faunas repres
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