142 MAURICE G. MEHL 



greater wings of the sphenoid is a circular excavation 26 mm. in 

 diameter. Although shallow the depth of the excavation is accen- 

 tuated by a prominent curved ridge on either side springing from 

 the base of the occipital condyle. 



THE POSTERIOR ASPECT 



In a posterior view Angistorhinus resembles in the general form 

 Lophoprosopus^ (Phytosaurus) kapffi H. von Meyer^ or Mesorhinus 

 Fraasi. It is depressed in appearance as the skull is over twice as 

 wide as high. From the lowest point of the quadrates to the plane 

 of the dorsal surface it measures about 166 mm. Between the lower, 

 lateral angles of the quadrates the width is about 386 mm. The 

 post-temporal fenestrae are exceptionally large, perhaps larger than 

 in any other form. Those in Lophoprosopus kapffi (see reference 

 above) are about 32 mm., while in A. grandis they measure nearly 

 40 mm. The width is about 11 mm. From the outer extremities 

 of these openings, which are about 180 mm. apart, they are directed 

 inward and slightly down. The foramen magnum is smaller than 

 in most of the phytosaurs, about 20 mm. in diameter. The quad- 

 rate foramina lie between the quadratojugal-quadrate union, about 

 46 mm. above the lower face of the quadrates. They are oval in 

 shape, the vertical diameter being 23 mm., the lesser diameter about 

 II mm. The outer border of these foramina is formed by the 

 quadratojugals, the inner border apparently by the quadrate alone. 

 One of the most remarkable features seen in the skull of A . grandis 

 is the difference between this form and most of the other phyto- 

 saurian genera in the upper posterior border of the skull. In 

 Lophoprosopus, Mystriosuchus, and other forms, perhaps, the parieto- 

 squamosal arcade, bounding the upper temporal vacuity posteriorly, 

 is considerably reduced and depressed. Quoting McGregor on this 

 point in Mystriosuchus planirostris Fraas •? 



A casual observation of the dorsal surface of the skull might lead the 

 observer to think that the supratemporal fenestra was incomplete posteriorly, 



' The substitution of Lophoprosopus for Phytosaurus is explained in the appended 

 list of genera and species. 



^ McGregor, Memoirs of the Amer. Mas. Nat. Hist., Vol. IX, Part II (1896), 

 p. 45, Fig. 4. 



3 Ibid., p. 46. 



