306 Herr F. Slebenrock on the 



a pit. In the latter lies on both sides the foramen caroticum 

 internum. The cylindrical processes form the floor of the 

 fossa hypophyseos, in the roof of which on each side, conse- 

 quently at the base of the processus alares, is situated the 

 foramen for a branch of the internal carotid, which opens into 

 the cranial cavity on the upper surface of the basisphenoid by 

 the hole already mentioned. On the under surface of the 

 basisphenoid between the processus pterygoidei arises the 

 parasphenoid ; this extends forwards below the cylindrical 

 processes as a narrow dagger-like bone. Its free portion is 

 somewhat longer than the body of the basisphenoid. Fritsch 

 [loc. cit.) and liaur {he. cit.) iiave expressed the conjecture 

 that the parasphenoid, forming tlie entire under portion of the 

 basisphenoid together with the processes which project back- 

 wards, in very young individuals admits of being separated 

 from the basisphenoid as an independent bone, I thoroughly 

 concur in this view, since on the underside of thebasisplienoid 

 it is possible to trace almost the entire outline of the para- 

 sphenoid ; only, in my opinion, Fritsch is mistaken in 

 believing that the processes for attachment to the pterygoids 

 also belong to the parasphenoid. It has been shown by 

 Parker* that the basisphenoid is formed by the union of 

 three ossifications, the lateral ones of wiiich are the processus 

 pterygoidei. Moreover the parasphenoidal plate is separated 

 from the base of the processus pterygoitleus by a cleft, so that 

 as a matter of fact no connexion exists between the bony 

 parts in question. In this cleft lies the posterior foramen 

 caroticum internum. 



In the lizards we find in the fossa hypophyseos three pairs 

 of aj)ertures : in front on both sides of tlie cylindrical processes 

 the foramen canalis Vitliani anterius, behind at the bottom of 

 the fossa the foramen caroticum internum, and at the side and 

 above the foramen tur a branch of tlie internal carotid. 

 Hatteria^ however, like the Chelonians, possesses only two 

 ])airs of apertures in the fossa hypophyseos, since the foramen 

 canalis Vitliani anterius is absent, iiere we have a further 

 character in which llatteria recedes from the lizards and 

 approaches the Chelonians in the structure of the head. 



The otosphenoid is a quadrangular bone, the upper angles 

 and the inferior anterior angle of which are produced into 

 processes, while the inferior posterior angle remains blunt. 

 The upjjcr border unites with the supraoccipital ; its posterior 

 end is produced into a nnxlerately long, triangular, |)ointed 

 i)rocess, the processus post>,Mior, which is apj)liril like a scale 



* W. K. I'lirlvcr and (i. .1. l^ottany. 'The Morpliolniry of the Skull' 

 (l.Diulun, 1H77) : (Jenuaii triinslalion by 15. Vetter, 1>>71». 



