Osteohujtj of the //(«'/ p/IIattciia. 299 



caitila^'inous and is cldsdy applied to the cpiptcrygoid- 

 colimu'lla, but no fiirtlicr detaiLs are j^iven. The presence of 

 an orbitosplienoid in llntteria is likewise pointed out by 

 Cope*, thouf^li it would follow from the author's statement 

 that the structure in question is bony and not cartilaginous ; 

 for upon page 189 he writes that in the membranous cranial 

 wall in lizanls an ossification occurs, upon which he bestows 

 the provisional designation " postoptic," and does not term it 

 the alisphenoid, like Parker, since, according to his view, 

 the cpiptcrygoid-columella is the real alisphenoid. Coming 

 to Ilatteria, he then proceeds to say : — " In the Rhyncho- 

 cephalian genus Sphenodon these two elements \_i. e. the post- 

 optic and ej)i|)terygoid] coexist with an orbitosplienoid, lying 

 between the optic and trigeminal foramina. The two together 

 may be homologous with the mammalian alisphenoid." 1 am 

 not of this oj)inion, since the orbitosphenoid is in the case of 

 llutteria precisely as in that of the other lizards, if it occurs 

 at all, without any connexion with the epipterygoid-columella, 

 and remains in a cartilaginous state througliout life. It is 

 semilunar in shape, and forms with the posterior notched edge 

 of the presphenoid, with which it is united above and below, 

 an oval hole, the optic foramen, for the exit of the optic 

 nerve. 



From the upper third of the posterior edge of the orbito- 

 sphenoid a stout cartilaginous process projects backwards and 

 somewhat u])wards, and then divides into two thinner rami. 

 Of these the uppermost and shorter has an anterior and 

 upward direction ; it runs to the first postfrontal and unites 

 with the upper trabecula. The lower and considerably longer 

 ramus trends downwards and backwards, and runs almost 

 parallel with the lower portion of the cartilaginous orbito- 

 sphenoid ; it unites with the processus anterior inferior of the 

 otosphenoid and with the processus alaris of the basisphenoid. 



It follows from what has just been stated that the orbito- 

 sphenoid is not embedded in the anterior cranial wall in 

 complete isolation, but is in intimate connexion with the bony 

 sphenoid group and with the roofing bones of the head. 



The anterior cranial wall, which is cartilaginous in Ilat- 

 teriGy is fixed to the crista cranii frontalis, and passes forwards 

 in the shape of a narrower canal to the olfactory cavity ; 

 where, however, it expands once more in an aliform manner, 

 since it reaches down on each side on the inner edge of the 

 prefrontal as far as the anterior extremity of the palatine, 

 and thus forms the optic-nasal septum. The groove itself 



* E. Cope, " The Osteology' of tlie Lacerlilia " (reprinted May 10, 1892, 

 from Proc. Amer. Phil. !Soc, vol. xxx.j. 



20* 



