56 



NEW REPTILES AND STEGOCEPHALIANS FROM 



pterygoid and the palatines is not found in any other form of the Parasuchia. In 

 Promystriosuchus there is a strong external process of the pterygoids which is underlain 

 by the posterior end of the transverse; the palatine vacuity is represented by a small 

 foramen between the palatine and the transverse, which appears on the lower surface 

 near the posterior end of the transverse. 



The primitive characters of Promystriosuchus appear in the elevated parieto-squamo- 

 sal arch, the relatively anterior position of the narial opening,' and the elongation of the 

 parasphenoid process. The other characters cited are those of the more specialized 

 Parasuchia, and it is evident that the form here described must be placed in the Mystrio- 

 suchid group of the Phytosauridse. The primitive characters are conservative features 

 which are found in at least one other member of the same group and family. 



Comparison with Angistorhinus. 



Angistorhinus'^ is in many ways the nearest known form to Promystriosuchus. 

 A consideration of the comparative characters will make more evident the similarities 



F iG. 22. — Angistorhinus, lateral view of skull, after Mehl. 



A. Lateral view of skull. 



B. Upper view of skull. 



C. Lower view of skull. 



D. Posterior view of skull, somewhat larger. 

 smx., septomaxillary. Other lettering as usual. 



and differences between Promystriosuchus and the other Mystriosuchids. The relative 

 proportions in length of the prenarial and postnarial portions of the skull of Angistorhinus 

 are as 10 : 6.4, or approximately 5 : 3; the antorbital vacuity is elongate and extends as 

 far forward as the anterior edge of the narial opening; the opening is surrounded by a 



1 Huenc, in the Gcol. u. Paleont. Abhdlg., N. F., Bd. x, Hft. 1, s. 53, has suggested that the position of the 

 narial opening and the elongation of (he rostrum are two distinct things and that the retreat of the nares is connected 

 with the shortening of the posterior part of the skull. The relation between the antorbital vacuity and the nares is 

 regarded by him as a phylogenetio character; as the nures retreated the antorbital opening would appear more and 

 more anteriorly in the skull. 



^ Mehl, M. G., Journal of Geology, vol. 21, No. 2, p. 186, 1913; Ihid., vol. 23, No. 2, p. 129, 1915. 



