122 PATAGONIAN EXPEDITIONS! PAL/EONTOLOGY. 



downward-projecting spine, which overhangs the optic foramen ; in 

 todon this ridge is very prominent. 



The nasals are short and broad, though much longer than in the 

 Pampean glyptodonts ; they are convex transversely, nearly plane longi- 

 tudinally, and, projecting beyond the premaxillae, end in bluntly rounded 

 tips. The anterior nares have much the same shape as in Glyptodon, but 

 are somewhat smaller and broaden less toward the dorsal side. As in the 

 latter genus, a stout bony septum divides the nasal passage into two 

 parts and extends from the nasals to the hard palate. The premaxillaries 

 are very small, but far less reduced than in the Pampean genera; the 

 horizontal ramus is short, thin and weak and, with its fellow, forms a 

 rounded anterior termination to the hard palate, and each is perforated by 

 a very small incisive foramen; the ascending ramus is a narrow strip, 

 which extends to the nasal, excluding the maxillary from the border of 

 the anterior nares, while in all the Pampean genera it is widely separated 

 from the nasal. The maxillary is very large, and, though attaining no such 

 extraordinary proportions as in Glyptodon, is very long and deep ; the 

 preorbital portion, which is relatively much longer than in the latter, 

 varies considerably in length in the different species and individuals ; the 

 zygomatic process forms a very long, descending plate, with its broader 

 side turned forward and ending distally in a rounded border. In corre- 

 lation with the increased depth of the jaws, this process is far longer in 

 Glyptodon. The bony palate is very long and narrow and of nearly 

 uniform width throughout ; transversely it is concave, but longitudinally 

 it is concave in front, convex and rising steeply behind. The extent of 

 the palatines is not determinable in any specimen that I have examined. 

 The posterior narial opening resembles that of Glyptodon, but is lower, 

 and presents almost directly backward. The pterygoids form broad, 

 rugose surfaces, without fossae or hamular processes. 



The mandible displays the curious features of the Pampean genera, but 

 in a much less pronounced degree. The horizontal ramus is rather short, 

 laterally compressed and deep, coossified at the symphysis, where the 

 edentulous part of the alveolar border is flared outward to form the spout 

 which is so characteristic of all the glyptodonts, but does not project so far 

 in front of the premaxillae as it does in the Pleistocene types. This feature 

 is not visible in the specimen figured in Plate XXIII, fig. i, the symphysis 

 of which has been destroyed, but is well shown in Lydekker's plate ('94, 



