ADMEASUREMENTS OF THE CRANIUM OF TOXODON. feet inches lines Extreme length 2 4 Extreme breadth 1 4 Extreme height, (exclusive of the lower jaw) 10 Length of zygomatic process 1 1 6 Depth or vertical extent of do. 6 Transverse extent of zygomatic fossa 6 Transverse diameter of cranium between the zygomatic arches 5 Transverse diameter of occipital plane of the cranium 1 From the outside of one condyle to that of the opposite condyle 8 6 Length of the bony palate 1 6 Extreme breadth of ditto 6 Breadth of palate at the intermaxillary suture 2 6 Breadth of palate behind the molar alveoli 3 Longitudinal extent of the molar alveoli 9 6 Longitudinal extent of the diastema 5 6 Transverse diameter of posterior nasal aperture 3 9 Transverse diameter of occipital foramen 3 Transverse diameter of glenoid cavity 4 6 Antero-posterior do. of ditto 1 DESCRIPTION OF FRAGMENTS OF A LOWER JAW AND TEETH OF A TOXODON. Found at Bahia Blanca, in latitude 39° on the East coast of South America. In looking over some fragments of jaws and teeth, forming part of Mr. Darwin’s collection of South American mammiferous remains, and which had been set aside with mutilated specimens referrible to species belonging to the family of Edentata, my attention was caught by the appearance of roots of teeth projecting, in a different direction from the grinders, from the fractured anterior extremity of a lower jaw, and I was induced to examine minutely the structure of the teeth in this specimen, and to search the collection for corresponding fragments. The result was the discovery of portions of the two rami, and the commencement of the symphysis of a lower jaw, containing anteriorly the roots of six incisors, and at least six molars on each side; but as the rami had been fractured through the middle of the sixth alveolus, the number of grinders may have corresponded with those in the upper jaw of the Toxodon.