82 PATAGONIAN EXPEDITIONS I PAL/EONTOLOGY. 



portion of the rostrum, curving far over upon the dorsal side. The max- 

 illaries are exceeding long and low, forming much the greater part of the 

 rostrum, upon the dorsal side of which they are reflected. Enough 

 remains of the palate to show that it is very long and remarkably narrow, 

 broadening slightly behind. 



The mandible is quite peculiar; the horizontal ramus is rather shallow 

 and for most of its length thick and stout, but becoming very much com- 

 pressed, thin and plate-like in the anterior part, where it is very different 

 from the slender and tapering ramus of Prozaedius, one of the most con- 

 stant and characteristic differences between the two genera. Two mental 

 foramina are present, of which the anterior one is very large and deep 

 and is placed below 2, while the posterior one is very much smaller and 

 opens below -3. The ventral border of the jaw is straighter than in the 

 last named genus, but rises more and is more concave below the ascend- 

 ing ramus, which is more steeply inclined ; the condyle is large and 

 concave. 



Vertebra, Ribs and Sternum. Of the vertebral column are preserved 

 the cervical and five thoracic vertebrae of one individual, three lumbars, 

 most of the sacrum and a few scattered caudals of another. The atlas 

 differs from that of Prozaedius only in size, but the axis is coossified 

 with both third and fourth cervicals, instead of with the third only ; the 

 fifth, sixth and seventh are relatively longer and have stouter neural 

 arches. 



The thoracic vertebras exhibit no features that call for description, while 

 the lumbars and sacrals (Plate VI, fig. 25) hardly differ from those of 

 Prozaedius except in size ; however, it may be noted that the ends of the 

 lumbar metapophyses are expanded antero-posteriorly in an unusual 

 degree. The caudals, which are in an unsatisfactory state of preservation, 

 indicate a long and stout tail. 



No exact comparison of the ribs with those of Prozaedius can be made, 

 but in the present genus they appear to be relatively broader. The manu- 

 brium sterni is like that of the former, but with much more prominent 

 ventral keel, and with more elongate extension behind the processes for 

 the first pair of ribs. 



Appendicular Skeleton. A fragment of the distal end of the scapula is 

 remarkable for the great development of the posterior ridge, which is com- 

 parable to the true spine in prominence and is quite distinct from the 



