68 NEW REPTILES AND STEGOCEPHALIANS FROM 



these sockets the premaxillary narrows, and there are three small sockets, rather on the 

 side of the bone than on its lower surface. There are 23 sockets in the premaxillary; in 

 the anterior portion these are rather more on the side of the bone, but by the middle of 

 the series they come to lie entirely on the lower surface. The middle of the snout is 

 occupied by the two prominent rounded ridges which are considered to have acted as 

 buffers to prevent injury to the jaws when they were snapped violently together. 



The second skull (Leptosuchus imperfecta, No. 7523, University of Michigan) 

 is much larger than the first, measuring approximately 112 cm. over all. There is a 

 break in the continuity of the snout, and it is impossible to determine the exact length, 

 though only a very small part, if any, can be missing. The whole skull seems propor- 

 tionately stouter than that of the smaller skull. As certain portions must be restored, 

 it is desirable to designate this as a new .species only tentatively, until more detailed 

 study can be made. One very remarkable feature appears in this skull: There is an 

 elevation on the upper surface of the snout, somewhat farther back than in the others 

 in the collection. This elevation is decidedly rugose and its upper surface is excavated 

 by a nearly hemispherical pit with a smooth inner surface. The pit is 5 cm. long and 

 4 cm. wide, extending into the symphysis of the premaxillary bones. The condition is 

 so remarkable and unexpected that the pit was at first taken for the opening of the 

 external nares, but this is easily demonstrated to be impossible, v. Huene 1 described 

 a somewhat similar condition in a specimen of M. pleiningeri. There is, in his speci- 

 men, a rough area near the anterior end, which he attributed to a fracture or injury. 

 In the center of this rough area he found a nodule of matrix. From the evidence cited 

 in this paper it is apparent that an elevation on the premaxillary portion of the snout of 

 members of the Mystriosuchid group of Phytosaurs is a normal thing, but in none of 

 the other specimens is there any evidence of a pit. The region of the snout surround- 

 ing the pit is rugose, but without any evidence of fracture or injury. The meaning 

 of this apparent abnormality is at present entirely conjectural. 



Contrasting characters in the skulls of the known Phytosaurs.- 

 Paleorhinus: 



1. Post-temporal arcade depressed. 



2. Antorbital opening posterior to the external nares rounded. 



3. Length of the prenarial portion of skull is to the postnarial portion as 1+ : 1. 



4. Post-temporal fenestra small. 



5. Posterior bar of parietal short. 



6. External nares with elevated rim; internal nares posterior to external. 



7. Squamosals not greatly extended behind. 



8. Orbits look up and out. 



9. Septomaxillary (?). 



10. Premaxillary and maxillary teeth 36, rounded in section. 



11. Palatines with inner edge elevated into a ridge. Palatine vacuity anterior to the middle of the transverse. 



12. Transverse overlaps the external pterygoid process below. 



13. Vomers extend back to interpterygoid vacuity. 



14. Parasphenoid process short (?). 



15. Interpterygoid vacuity small. 

 Angistorhinus: 



1. Post-temporal arcade at the level of the top of the skull. 



2. Antorbital opening with the anterior end even with the anterior end of the external nares. Oval. Anterior 



end acute, posterior end rounded. 



3. Length of the prenarial portion of the skull is to the postnarial as 5 : 3. 



4. Post-temporal fenestra largest of any known form. 



5. Posterior bar of the parietal very short. 



6. External nares with elevated rim, low septum; internal nares a little posterior to the external. 



7. Squamosal considerably extended backward and with a strong descending hook; overhangs the bones below. 



8. Orbits look upward more than outward. 



1 Huene, F. v., Beitriige zur Kenntnis und Beurtheilung der Parasuchier, Geolog. u. Paleontlg. Abhand- 



lungen, N. F., Bd. x, s. 5, fig. 2, 1911. 



2 The same character is described under the same number under each genus. The characters given are as 



described by the authors. Some of these must be modified by further study. The probable errors are 

 in the description of the palatal region. 



