50 MR. E. P. ALLIS ON POSTORBITAL ARTICULATION OF 



disappearance ofa musculus levator arcus palatini. The processus 

 oticus is part of the epipterygoid bone and lies anterior and 

 internal to this process of the pterygoid. 



In the Sauria the processus basalis of fishes must certainly be 

 represented in the meniscus pterygoideus, but whether the 

 processus basalis of recent Amphibia is represented in the meniscus 

 alone, or in that structure together with the processus basiptery- 

 goideus, would seem to be an open question. Regarding the 

 development of these structures in the Sauria, Gaupp says (1905, 

 p. 762) that they are both represented, in young embryos of 

 Lacerta, by a mass of dense tissue which lies between the foot of 

 the processus ascendens and the root of the trabecula, and is 

 more closely connected with the former than with the latter. 

 When chondrification takes place, this mass separates into two 

 parts, the mesial one chondrifying as a laterally directed process 

 of the trabecula (the processus basipterygoideus) and the lateral 

 one becoming the meniscus. This manner of development of 

 these two structures in this reptile, and their relations to the 

 ascending process of the palatoquadrate, led me to suggest, in an 

 earlier work, that the mass of tissue referred to might represent 

 the pharyngeal element of the mandibular arch. 



In the adult Lacerta, the meniscus lies on the mesial aspect of 

 the Os pterygoideum (Gaupp, 1905, p. 767), and between it and 

 the processus basipterygoideus an articular joint is formed, the 

 palatoquadrate being movable. In Sphenodon, the meniscus and 

 the processus basipterygoideus are also both found (Howes and 

 Swinnerton, 1901), and there is an articular joint between them, 

 as in Lacerta, but whether the palatoquadrate of this reptile is 

 movable, or not, I do not find definitely stated. A mesial process 

 of the Os pterygoideum is shown by Fuchs (1901), in an embryo 

 of this reptile, projecting mesially along the ventral surface of 

 the processus basipterygoideus, and it would seem as if it must 

 interfere with any movement, if it does not actually prevent it. 

 Broom (1922) says that Parker described a meniscus, in 1878, in 

 a fairly advanced specimen of Zootoca, and he himself describes it 

 in a la.rval Agama hispida, where it lies, as in Lacerta, between a 

 cartilaginous processus basipterygoideus and a dermal pterygoid 

 bone. The articular joint is between the meniscus and the 

 processus basipterj^goideus, and Broom considers the meniscus to 

 be the homologue of the mesopterygoid of fishes, basing this 

 conclusion on the conditions found in Eusthenopteron, a fossil 

 Rhipidistid described by Bryant (1919). The so-called meso- 

 pterygoid of the latter fish, as shown in the figure reproduced by 

 Broom, is, however, called by Bryant a meta pterygoid, and that 

 part of the bone that has the marked upward extension shown in 

 the latter author's text-fig. 6 would seem to be a pi-ocessus 

 metapterygoideus metapterygoidei. 



From the above references to the conditions in certain of the 

 Amphibia and Reptilia it is seen that, in these animals, the 

 existing postorbital articulation of the palatoquadrate with the 



