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Show 85 ainel, is triangular in section, and somewhat curved in its long axis. A convex face is directed forward and outward, ( on the supposition that the tooth is superior,) and a nearly plane face posteriorly. The inner face is worn flat by the attrition of an opposing tooth. The pulp- cavity is minute or wanting. Char, specif.- The pitting of the maxillary bone is not linear, and is sometimes, round; it is rather femote. The outside of the bone is steep, indicating that the muzzle is not depressed. Its face is swollen opposite the supposed canine tooth. The alveolae are round and longitudinally oval. The alveolar face is decurved near the end of the muzzle. The superficial layer of the cranial and dermal bones is dense and finegrained. The second series of specimens, whose reference is by no means certain, but which contains a dermal bone like that of the type, includes fragments apparently of the upper surface of the cranium. This is marked with irregular tuberosities and excavations resembling that seen in the Belodonta, of the Carolinian and Wtirtembergian Trias. A section of a narrow, dermal bone displays an elevated, obtuse, median keel, the only one which displays this form in the collection, the usual form being either fiat or slightly concave. Accompanying the same are numerous coprolites, which arc* apparently too small for au animal of the dimensions of the type- specimen. They are slender, and display rectal folds, which do not display a continuous spiral. They are found, wherever fractured,' to be filled with the rhomboganoid scales of some small fish. • Measurements. M. Length of fragment of maxillary 095 Depth ( oblique) atnostril( f) 050 Depth ( vertical) at nostril ( f) 045 Width ( median) at nostril (!).*. 025 Width at front alveolus 035 Diameter of canine alveolus r 015 Diameter of another alveolus 011 Diameter of centrum of ( f caudal) vertebrae < ^ 3f^ i ™ 6 " *. 022 Thickness of dermal shield 008 Measurement across four fossae 020- Diameter of crown of tooth No. 2 018 Length of coprolite of No. 2 045 Diameter of coprolite of No. 2 011 The flat and regularly- pitted dermal shields distinguish this genus from Belodon. The species was of large size; the cranial fragments equalling corresponding portions of the Gangetic Gavial. The evidence derived from the Typothorax coccinarum is favorable to the identification of this horizon with that of the Trias, although it cannot, of course, be regarded as conclusive nntil more perfect specimens are obtained. Besides the overlying sandstone bed. the red marls are traversed below it by a conglomerate, which* is in some places of a bluish tint. At some points, it weathers to* gravel, and near this horizon the vertebrate remains occur. At other points, it forms a very hard Potomac marble, containing pebbles of various colors. Near the same level I obtained specimens of impure copper- ore, which simulate petrified wood in form. The sandstones, especially those lying obliquely on the mountain- side, ( Fig. 7,) I found to contain obscure vegetable remains, some of which are replaced by oxide of iron. They reminded me of similar remains observed in the same horizon near Taos. On passing a mile to the south of the locality which has been described, the opposite masses of the Jurassic and Triassic rocks are seen to descend at an angle of 20° and 25° to the south, marking the terminus of another longitudinal wave of the axis, of which the one immediately to the north has been described in connection with Fig, 5. The valley caused by this descent is the drainage- axis of the Upper Gallinas Creek,, which issues from the mountains at this point. This locality is instructive as furnishing the third example of the fault existing between the Triassic and Jurassic rocks, already illustrated in Figs. 6 and 16. The Triassic sandstone is also faulted at several points at right angles to the principal fault, as seen in the north and south escarpment, ( Fig. 9.) The fragments of the fractured sandstone- bed strew the west slope of the Triassic mountain, and disappear in the red marls. * From this depression the mountain rises gradually first in a lower ridge and then to the long and regular crest of the Nacimiento Mountain, ( Fig. 10.) The axis of this new elevation forms an open angle with that of the range of the Gallinas proper, running northeast and southwest, the consequence of which is a change of strike of all the elevated beds on its flanks. The Cretaceous hog- backs make a very regular angle in their direction; its apex being the point of change of axis at the cove 1 have described above in detail. At the same time, the hog- backs approaoh nearer to the mountains, and the variegated and gypsum beds of the Jurassic are not |