1926] Hall: Sliill of the Bodent OtospcrmopliUus (jrammitrHs beecheyi 



375 



sutures separating them from the palatines can usually be made out 

 in ^. At this time the pterygoids are very thin and have actually 

 decreased in bulk. Their lengths in millimeters in several skulls are : 

 C,3; F, 8.6; I, 9; Q, 10.4. Instead of ending in a single point, the 

 hamular process of each pterygoid has two divisions, as shown in 

 figure 22. 



Fig. 22. External view 

 of right pterygoid process 

 of Q. X 2. 



Fig. 23. Ventral view of 

 vomer in a skull from the 

 same litter as B. X 12. 



Vomer and etJunoids. — Figure 23 shows the condition of the vomer 

 in a skull from the same litter as B. The two lateral wings are very 

 thin and are turned up at the lateral margins, M'hich are in contact 

 with the maxillae. A considerable area of cartilage separates the 

 posterior border of the vomer from the ossified portion of the pre- 

 sphenoid. On the anterior portion of the vomer a round column of 

 bone rises from the horizontal surface and establishes contact with 

 the maxillae at the posterior borders of the anterior palatine foramina. 

 In a skull from the same litter as F, and approximately of the same 

 age, the vomer is modified from the condition found in the skull from 

 the same litter as B. In the older of these two skulls the vomer and 

 rostrum are more elongated than in the younger. The column of 

 bone that rises from the horizontal surface of the vomer and meets 

 the maxillae is relatively shorter, but wider, in the older of the two 

 stages mentioned above. The thickness of the vomer seems to be not 

 much greater than in the younger skull. Posteriorly, in the skull 

 from the same litter as F, the vomer is not in contact with the pre- 

 sphenoid. Other skulls of greater age show that the vomer is always 

 a very thin element and that it is somewhat modified by the develop- 

 ment of the turbinal and ethmoid elements. In the embryo skull of 

 the same age as B these elements are little developed. In the skull 

 of the same age as F, the maxilloturbinals, nasoturbinals, and four 

 primary divisions of the endoturbinals are present in a well developed 

 state, but all lack the complexity of the adult condition. The por- 



