ME. T. ATTHEY ON PTEEOPLAX COENUTA. 179 



external to this they articulate with the postfrontals, the posterior 

 extremity of each frontal being received into an angle formed 

 by the parietals and postf rentals. 



Tlie parietals occupy the chief part of the middle region of the 

 cranium, and are of a triangular form, the base being posterior. 

 In the middle of the median suture is the oval parietal foramen. 

 It is large, being two-tenths of an inch in length, and rather 

 more than one-tenth of an inch in breadth ; it is surrounded by 

 an elongated oval space, which is somewhat elevated, the bone 

 here being thick and strong; and outside of this is a depression 

 of the same form, gradually rising outwards to the ordinary level 

 of the surface of the skull. At the anterior part of the parietals 

 the median suture has an irregular course to the left, no doubt a 

 mere individual irregularity. On their outer borders these bones 

 articulate, from front to back, successively with the postfrontals, 

 the postorbitals, the squamous, the epiotic, and the so-called su- 

 praoccipitals which lie behind them. 



The postfrontals are narrow, curved, and elongated, pointed in 

 front, where they abut upon the frontals, and broader behind, 

 where they meet the postorbitals ; their internal borders, irre- 

 gularly convex, articulate with the frontals and parietals ; their 

 external borders form the greater part of the concave and smooth 

 inner margin of the orbits. 



The prefrontals, which may have formed the anterior part of 

 the inner margin of the orbits, and the lachrymals are absent. 



The postorbitals, articulating in front with the postfrontals, 

 internally with the parietals, and posteriorly with the squamous, 

 are short thick bones which form the posterior part of the inner 

 orbital margin, and present an external projection which marks 

 the termination of that margin and to which, as well as to the 

 similar process on the postfi'ontal, ligaments and other structures 

 forming the outer wall of the orbit were attached. Behind these 

 projections the borders of the postorbitals, as they go to join the 

 squamous, arc concave. 



The squamous, a little larger than the last, are four-sided : \\\o 

 external side is convex, longer than the others, and tlu^ up])or 



