The Chondroer allium of an Embryo Pig. 197 



cavity in the reptiles (Fig. 7) ; (2) the location of the ganglion 

 semilimare (Gasseri) outside the cranial cavity in the reptiles and 

 within it in the mammals; (3) the formation of a part of the side 

 wall of the brain-case (ala temporalis) in the chondrocrania of the 

 mammals at some distance outside the general surface of the brain- 

 box; (4) the vestiges of the primitive side wall which are still 

 present in the mammals; (5) the homology of the ala temporalis 

 with the reptilian processus basipterygoideus. For a full discussion 

 of these points I would refer to Gaupp's papers of 1900 and 1902. 

 Sus offers another vestige of the primitive side wall which is not 

 mentioned by Gaupp, namely the connective between the front end 

 of the ear-capsule (pars cochlearis) and the lateral end of the 

 processus clinoidcus posterior, forming the secondary foramen for 

 the nervus abducens. Among the vestiges which he mentions and 

 which are not present in Sus are the tcenia interclinoidea, often 

 present in the primates, and the tcenia clino-orbitalis of Echidna. 

 The separate pterygoid cartilage pieces which have been described 

 in Talpa, Lepus, Tarsius and the apes, and which Parker mentions 

 in an older stage of Sus (external pterygoid plates), are here only in 

 the precartilaginous condition. 



The character of the ala orhitalis, or anterior v/ing of the orbito- 

 temporal region, is that of the generalized mammalian type. The 

 two roots, which are pressed close together in Talpa, are here well 

 separated by the large foramen opticum, and, therefore, the two 

 roots can rightly be called tcimia prooptica and tcenia metaptica. Be- 

 tween the two optic foramina the median basal cartilage shows a 

 shallow transverse furrow, the sulcus chiasmatis. A small process 

 on the ventral side of the posterior root serves for the attachment of 

 some of the eye muscles. The two roots soon join outwardly enclos- 

 ing the optic foramen and, expanding, form the ala orbitalis ( Frontal- 

 pi atte of Spondli), the homolog of the reptilian planum supraseptalc. 

 This unites anteriorly with the nasal capsule and posteriorly with 

 the lamina parietalis. The latter connection, the commissura orbito- 

 parietalis, is broad (PI. Ill) and similar to the corresponding com- 

 missure in Echidna. This is, in all probability, a primitive condi- 

 tion, showing an approach to the solid side wall of the ancestors of 



