4l2 II B- POLLARD. 



of these bones is indicated in both directions. In spite of Fraas' 

 denial, the bone bounding the vagus foramen externally must be con- 

 sidered as a fused exoccipital und opisthotic (or petrosum). In old 

 si)ecimens of Folypterns the suture between the two elements is al- 

 most completely obliterated and the opisthotic passes upward and back- 

 ward supporting the posttemporal scale, being tied to it in the young 

 specimens by a stout ligament, in old by a bone arising in that liga- 

 ment. The posttemporal scale corresponds in all relations to the epiotic 

 of Stegocephali and thus we see that the transition to Mastodonsaurns 

 is by the disappearance of the ligaments, while to Cyclotosaurus it is 

 by enlargement of the bone arising in the ligament. 



Palatal Region (fig. 15). 



In addition to the bones of the palate described by Traquair 

 there is in front of the parasphenoid a small median un- 

 paired bone formed by the fusion of the bones of several small 

 teeth, the lowest number observed being 4. The parasphenoid continues 

 forward dorsally to it as a spicule underlying the nasal septum. In 

 a short previous notice I have called the unpaired bone vomer though 

 the adjoining paired bones correspond to the vomer of Urodeles which 

 I have called dermopalatines. If this homology is pushed further one 

 comes to the conclusion that the vomer of Mammalia is a dermopala- 

 tine a reversing of names which is not justifiable. Therefore it must 

 be concluded that this bone which seems unpaired ab origine is a 

 new bone comparable to the dermethmoid above and which , only 

 doubtfully reappears again in the animal kingdom. One may call it a 

 dermal subrostral. 



The metapterygoid is purely a dermal bone and we have there- 

 fore paired metapterygoids, ectopterygoids, entopterygoids, vomers and 

 an unpaired parasphenoid and subrostral, ten bones in all in the pa- 

 late. The entopterygoid articulates far in froiit with the parasphenoid. 

 (Comparing the palatal bones of Polypterus with Branchlosmirus 

 or the frog (cf. especially liana pipiens Parker, Batrachia III) ani- 

 mals which I trust I have shown are certainly comi)arable with one 

 another, one sees that the space between the entopterygoid and para- 

 sphenoid in Folypterus has in the latter animals widened considerably 

 and forms the well known membranous i)ortion below the eye. If this 

 comparison is legitimate it will be seen that the entopterygoid be- 

 comes the palatine in these higher forms. The metapterygoid in 



