348 ON THE EXTINCT MAMMALIA OF 



triangular scroll descending by its base from the side of the basi-sphenoid and basi- 

 occipital, and curving outwardly to terminate in a free point. It reminds one of the 

 process developed from the alisphenoid, enclosing the front of the tympanic cavity, 

 in the Opossum. No auditory canal extends from the bulla in the fossil, but an open 

 archway communicates with its interior from between the post-glenoid and post- 

 auditory processes, as in the Opossum. 



The glenoid fossa forms a nearly level plane above, and behind descends almost at 

 a right angle upon a comparatively long, robust post-glenoid tubercle. This is verti- 

 cal and hooked inwardl3^ At its base internally there is a vascular foramen. 



The optic foramen holds a rather more advanced position than usual in its relation 

 with the spheno-orbital foramen. The latter, a short vidian canal, and the oval 

 foramina, hold the same relative position with one another as in the Dog. 



The position of the eustachian communication with the tympanic cavity and the 

 carotid canal appear to be at ihe fore and outer part of the scroll-like auditory bulla. 



The condyloid, jugular, and stylo-mastoid foramina hold the usual relative position 

 with one another. 



The palate is long, nari'ow, and moderately arched fore and aft and transversely. 

 No large perforations exist in it as in the Opossum. 



The palate plates of the palate bones together form a triangle with zig-zag sides 

 and a notched apex, which reaches as far forward as the fourth molars. 



The palatine notch resembles that of the Fox, being of considerable capacity and 

 extending as far forward as the interval between the last pair of molar teeth. It 

 there fonns a double festoon with a prominent median palate S2)ine. 



The posterior palatine foramen, about a line long, occupies the narrow triangle be- 

 tween the last molar tooth and the bottom of the palatine notch. Two other fora- 

 mina, quite small, occupy the vicinity of the lateral suture between the palate plates 

 of the palate and maxillary bones. 



The incisive foramina are small, not being quite a line in length. They are 

 situated between the position of the pair of incisors retained on each side. 



Forms and connections of the hones of the skull. — The supra-occipital extends a short 

 distance forward on the top of the cranium, and is defined by an anterior produced 

 convex border. The occipito-parietal suture from the top of the cranium curves out- 

 ward, backward, and downward, turns over the lateral edge of the inion to its poste- 

 rior surface, and descends to the pars mastoidea of the temporal. 



The pars mastoidea contributes a large surface to the lateral depression of the 

 inion, and is interposed between the supra-occipital and parietal above and the ex- 

 occipital and squamosal below. 



The supero-lateral margin of the inion is formed in succession by the supraroccipi- 



