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Show 1900.] FOSSIL MARSUPIAL FROM TASMANIA. 779 which meet the nasals and prevent the maxillae from comiug into contact with the frontals, (6) the great width of the nasals, (7) the very anterior position of the infraorbital foramen, and (8) the general massiveness. Owing to the base of the skull being broken, tbe length measurement from the basion to the gnathion cannot be taken, and therefore, for the purpose of comparison with other skulls, the total length from the posterior eud of the sagittal crest to the anterior end of the nasals, that is the total length along the mid-dorsal line, is taken. Though this is not so satisfactory as the former measurement, still it will serve to a certain extent as a basis of comparison. The total length is just 100 mm., and the greatest width across the zygomata is 67 m m . Taking the same length of various species of marsupials, measured for comparison, as 100, we find that the proportionate breadth is as follows :-Trichosurus fuligi-nosus 58"7, T. vulpecula 53-7, Pseudochirus herbertensis 60, P. archeri 63-8, P. cooki 53-7, Phascolarctos cinereus 59, Cuscus sp. 59, Bettoncgiapenicillata 56*3,Dendrolagus bennettianus55'7, Phascolomgs mitchelli 75-2, Dasgurus maculatus 68-2, Sarcophilus ursinus 77, Didelphys sp. 56*9. In regard to this it is intermediate between such extreme forms as Sarcophilus on the one hand and Petrogalc on the other, and approaches most nearly to Dasgurus, showing a decidedly greater width thau is met with in the Phalangeridae. The occipital region is separated from the upper surface of the skull by a well-marked lambdoidal crista which curves somewhat backward, so as to afford a concave surface for tbe muscles of the neck, the occipital plane sloping slightly downwards and forwards and not being vertical as in most marsupials. The curvature of the ridge is carried to about the same extent as it is in Dasgurus, the ridge of either side curving slightly towards the middle line. From a point just behind the intertemporal constriction a strongly marked sagittal crest runs backwards to the lambdoidal crista, the former being as well developed as in TJiylacinus and Dasyurus, In this respect the fossil offers a strong contrast to the Phalangeridae, in which the twTo temporal ridges run backwards converging towards the lambdoidal crista; so that no such sagittal crest is formed as is characteristic of the Dasyuridae, and is seen also in Didelphys marsupialis. On the upper surface of the frontals there is a shallow, but sharply outlined, depression, the converging margins of which are continuous posteriorly with the sagittal crest. The parietal suture extends about as far forwards as the latter. A very remarkable feature is the great extent and anterior extension of tbe squamosals, the anterior ends of which reach almost as far forwards as those of the parietals. An equally striking feature, and one in which the fossil agrees with Dasyurus aud Sarcophilus, is the general parallelism of the upper part of the suture of the squamosal with the sagittal crest. In such forms as the Phalangeridae for example the sutures show a continuous marked convergence towards the middle line posteriorly. In regard |
