BY W. J. McKAY. 937 



The pterygo-parietalis arises from the anterior portion of the 

 postero-lateral edge of the parietal, and from the lateral plate of 

 the parietal immediately below. It runs downwards, backwards 

 and outwards, to be inserted on the middle third of the external 

 edge of the pterygoid bone, and slightly into the posterior extremity 

 of the transverse bone. As the muscle passes backwards it is 

 closely connected with the external face of the spheno-pterygoid 

 muscle ; while the anterior temporal and parieto-mandibular muscle, 

 together with the branches of the fifth nerve, cover it externally. 



The muscle is very large in Dahoia and arises more anteriorly 

 than in Acanthojyhis. 



Cuvier regarded the muscle as a dismemberment of one of the 

 temporal group. From the relations of the nerve trunks to it, 

 we consider that it has no connection whatever with the temporal 

 muscles, and, as shown below, we believe it to be a specialised ten- 

 sor palati. The nerve of supply emerges behind the fifth, from a 

 foramen in the lower part of the alisphenoid, and occupies such a 

 position as the nerve for the otic ganglion does in the higher 

 animals. 



The muscle acts as a protractor of the pterygoid bone, and 

 therefore as an erector of the fangs. 



M. PARIETO-PALATINUS (part of the tensor palati). 



3f. 2^i^'^y90-sphenoidcclis anterior, Hoffmann ; Innerevo7'dere 

 Fliigelmuskel, D'Alton ; M. palatinus, Hiibner ; Pres2Jheno-pala- 

 tive, Owen ; Spheno^^cilatine, Duvernoy, R. Jones. 



The parieto-palatine muscle arises from the posterior concave 

 surface on the lateral plate of the parietal bone, and runs forwards, 

 downwards, and outwards, to be inserted on a small portion of 

 tlie pterygoid, and on to the posterior two-thirds of the palatine 

 bone. Some fibres may be traced to the mucous membrane 

 surrounding the fangs, here performing the office of retractors of 

 the membrane. The muscle lies at its origin between the parieto- 

 pterygoid and the ptery go-sphenoid muscles, and as it runs forward 

 it comes into relation with the fascia covering the lachrymal gland. 



