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Show 126 Measurements. * M. Length of last five molars 01* 50 Length of true- molar series : 0135 Length of last premolar .0060 Widthof last premolar 0050 Length of penultimate molar 0050 Widthof penultimate molar 0068 Width of last molar 0047 Length of last two inferior molars 0090 About the size of the domestic cat. PllOTOTOMUS INSFDJOSUS, Sp. tlOV. Represented in the collections of the survey by parts of the maxillary bone and both mandibular rami with teeth. The species is much less than the preceding, and differs materially in the forms of the teeth. The two anterior tubercles of the tubercular molars are similar and approximated; the posterior slightly divergent, and on the last tooth inclosing a third of small size. The last premolar has a broad heel and stout anterior cone, but no anterior tubercle. The tooth immediately precediug is much smaller, and also possesses a heel. The mandibular ramus is particularly slender, and the angle is not inflected. Measurement*. U. Length of last two inferior molars . 0060 Length of last molar 0034 Widthof last inferior molar 0020 Depth of ramus at last inferior molar 0045 Length of last premolar 0030 Elevation of last premolar 0028 PROTOTOMUS JARROVII, sp. nov. This Carnivore is of considerably larger proportions than either of the preceding. It is readily recognized as pertaining to the same genus by the identical form of the last two inferior molars, which are quite differeut from the corresponding ones in Oxyccna and other genera. These indeed, with the portion of the mandibular ramus which supports them, are the only well- preserved remains of this animal as yet in our possession. They indicate an animal of the size of the gray fox. In the last molar, the inner anterior tubercle is double, though low and obtuse. It differs from that in the species last enumerated in the presence of only two tubercles on the posterior portion of the crown instead of three, one being terminal and the other on the middle of the outer side. There are but two on the posterior end of the penultimate tooth, and all are low and unconnected excepting by the distinct rim of the crown. The center of the crown is thus concave. The rim is interrupted by notches between the tubercles on the outer side. No cingulum on inner, a weak one on outer side. Enamel smooth. The form of the molars is rather stout, and the ramus is thick and not deep, and - with broad, simple, lower border below the molars. Measurements. M. Length of last lower molar 0070 xuiAkU S anteriorly 0045 W K U i l ) posteriorly 0020 Width of penultimate behind 0050 Elevation of anterior ouap of last 0030 Depth of ramus at last molar 0140 This species is dedicated to my friend Henry C. Yarrow, M. D., to whom was committed the charge of that' party of the survey to which I was attached, and to whose zeal in the cause of the natural sciences the success of the special expedition is largely due. LlMXOCYON PROTEXUS, Sp. not. A civet- like Carnivore represented by one entire and a portion of the other mandibular ramus, with teeth well preserved, agrees iu generic characters with the species referred by Professor Marsh to his geuus Limnocyon, but differs from them all in its superior size. The molars are J, but the first molar is like the premolars of the Ca-nida, except in a slight widening of its posterior basis by the development of a broad ciiigulum on the inner side and round the basal lobe behind. From this point it extends forward on the outer side to the beginning of the auterior basal lobe, and there |