528 



torium and its continuation into the falx. The upper boundary of the rhinencephalic fossa 

 is much developed. 



Hunterian. 



3140. The right moiety of a vertically bisected cranium, from which the facial part 

 has been removed by a transverse section, of a Horse (Equus Caballus}. 



/ 



It shows the ossification which extends into the upper and back part of the tentorium, the 

 venous canal which extends from the lateral sinus to the temporal fossae, and the septa of the 

 frontal air-cells. 



Hunterian. 



The following specimens show some of the stages in the development and succession of the 

 teeth of the Horse (Eqims Caballus) : 



3141. The skull of a Filly or young Mare, with the deciduous teeth. 



The rudimentary canines are visible in the lower jaw, not in the upper one. The three 

 normal deciduous molars on each side are preceded by the first rudimental molar in both jaws : 

 this tooth is very minute in the lower jaw. The crown of the first true molar has been ex- 

 posed on the right side of the upper jaw. The exoccipitals have coalesced with the basi- 

 occipital, but not with each other or with the superoccipital. The suture is retained by which 

 the premaxillaries articulate with the maxillaries and the nasals, excluding the maxillaries from 

 the external nostrils. 



Presented by Henry Cline, Esq. 



3142. The right moiety of the facial part of a vertically bisected skull of a young 

 Mare. 



The three deciduous molars and first true molar are in place and use ; the second is begin- 

 ning to appear. 



Hunterian. 



3143. The skull of a young Horse, showing a similar stage of dentition. Purchased. 



3144. The skull of a Horse, of more advanced age. 



In this the first permanent incisor is in place in both the upper and lower jaws, but the 

 second and third permanent incisors have not displaced then- deciduous predecessors. The 

 crowns of the permanent canines are just visible. The first and second functional premolars 

 (p 2 &p 3) and the first and second true molars (m\ & TO 2) are in place. The anterior rudi- 

 mental premolar (pi) remains in the upper jaw, and a remnant of the last deciduous molar 

 is retained on each side of both jaws. The outer alveolar walls have been removed on the 

 right side of the upper jaw, where the crown of the last true molar is exposed in its forma- 

 tive socket. 



Purchased. 



