SCOTT : LITOPTERNA OF THE SANTA CRUZ BEDS. I 1 7 



diverging somewhat posteriorly and enclosing the front end of the narial 

 opening. Even in the oldest individuals, they display no tendency to 

 coossify. 



The bones of the hard palate are exceedingly thin and fragile and in 

 none of the specimens at my disposal are they in a satisfactory state 

 of preservation. Apparently, there are no incisive foramina, but merely 

 grooves in the position occupied normally by those foramina. In T. gracilis 

 Ameghino ('94(5, 32, fig. 9) figures very long, narrow foramina, separated 

 by a slender spine, but it seems likely that, in this instance, the draughts- 

 man was deceived by grooves filled with matrix. Lydekker's figure ('93, 

 XXVI, 2) would appear to be open to either interpretation. If, however, 

 no error be involved in Ameghino's figure, the presence of the incisive 

 foramina would sharply distinguish T. gracilis from the other species. 

 The maxillary part of the palate is of nearly uniform width between the 

 two parallel rows of teeth, broadening slightly in the anterior premolar 

 region. Shallow grooves run near the outer margins of the maxillary 

 palatine processes for nearly their entire length. At the anterior end of 

 these processes, as may be seen in Plate XVII, fig. i^, is a median open- 

 ing, continuing forward as the premaxillary grooves already mentioned. 

 Probably this opening served to transmit the blood-vessels and nerves which 

 ordinarily pass through the incisive foramina, but so distorted is this region 

 in even the best-preserved skulls, that I cannot feel entirely confident of 

 this interpretation. 



The palatines very early coalesce with the maxillaries and, even in 

 young animals retaining all of the milk-teeth, their limits are difficult of 

 determination. Apparently, however, they form a moderate portion of 

 the hard palate, with antero-posterior extent about equal to that of a molar 

 tooth ; the posterior palatine foramina, so far as can be judged from the 

 imperfect material, are entirely within the limits of the maxillaries. The 

 posterior nares are long, narrow and low, with nearly parallel walls ; the 

 front border is on a line with the middle of m-, while posteriorly the walls 

 arise opposite the middle of the glenoid cavities. The pterygoids termi- 

 nate in low, inconspicuous hamular processes, and the fossae are mere 

 grooves. The vomer is strongly developed and divides the forward part 

 of the posterior nares into two openings. 



Like so many other features of these more or less crushed and distorted 

 skulls, the cranial foramina are difficult to determine satisfactorily. So 



