150 Mr. T. Attliey on Aiitliracosaurus lUissclli. 



frontals for three fourths of their length, and to the postfrontals 

 for the remaining posterior fourth. 



27ie jyrefrontals are much broader than the frontals, by 

 which they arc bounded along the whole of their inner bor- 

 ders ; the lacrymals bound them in front, and the jugals on 

 tlieir outer borders ; they rest upon the postfrontals behind by 

 spaces not greater than f^ inch. The remaining parts of 

 their posterior borders form three fourths of the anterior mar- 

 gins of the orbital vacuities, including the greater part of the 

 two marginal concavities already noticed. 



The postfrontals, rather shorter and much narrower than the 

 last, which they join in front by a long process, articulate by 

 their inner edges for equal distances Avith the frontals and 

 parietals. Their anterior and outer borders form \-^ inch of 

 the posterior inner borders of the orbital vacuities, including 

 the posterior marginal prominence above mentioned. They 

 are bounded externally by the postorbitals and a small portion 

 of the supratemporals, and behind by the squamous bones. 



The squamous, of an irregularly square form, somewhat 

 concave internally and convex externally, are bounded inter- 

 nally by the parietals, anteriorly by the postfrontals, externally 

 by the supratemporals, and posteriorly by the epiotics and a 

 small portion of the so-called supraoccipitals. Their posterior 

 outer angles contribute the curved inner border of the channels 

 leading to the internal ears. 



TJie postorbitals are also of a somewhat irregularly square 

 outline, and their anterior borders form 1 inch of the posterior 

 and outer concave margins of the orbital vacuities. They are 

 united internally to the postfrontals, externally to the jugals, 

 and behind to the supratemporals. 



The jugals form large irregular triangles, the bases of which 

 lie along the maxilla, the truncated apices supplying about an 

 inch of the outer margins of the orbital vacuities, the posterior 

 angles being cut off by the quadrate-jugals. They are 

 7i inches in length, articulating anteriorly and internally with 

 the lacrymals and prefrontals, internally and posteriorly with 

 the postorbitals, the supratemporals, and, lastly, with the qua- 

 drate-jugal bones. 



The supratemporals, of in*egularly elongated form, lying 

 obliquely between the jugal and quadrate bones, and with them 

 constituting a good part of the lateral extensions of the cranium, 

 articulate anteriorly and internally with the postorbitals, exter- 

 nally with the jugals and quadrate-jugals ; posteriorly they 

 overlap and articulate with the quadrates, and on their inner 

 sides join, first, the postfrontals, and afterwards the squamous. 

 It may be noticed that, although the matrix is entirely cleared 



