Special Osteology. Sectorialia. 37 



to the large temporal muscles (the fossae from which these rise are 

 large and deep, and augmented by peripheral ridges of bone) ; there 

 is generally a process directed backwards from the angle of the jaw. 

 Acoustic bulled are commonly found, supported by the paroccipitals, 

 and developed either from the petrosal, or tympanic, or both, but 

 never from the Ali-sphenoid as in Thylacinus.^^ The Paroccipital and 

 Mastoid processes are sometimes distinct, sometimes connate, but 

 both tolerably developed. A narrow articular surface upon the Basi- 

 occipital is frequently found connecting the two condyles. The 

 Petrosals are generally perforated by the ento-carotids, and impressed 

 internally by a pit for the cerebellar ' flocculus.' The Tentorium is 

 always ossified, and usually the posterior part of the Falx also.f 

 The Rhin-encephalic fossae are generally well defined, and completely 

 divided both inter se by a thick Crista ff alii, and usually from the Pros- 

 encephalic compartment also by a low ridge. The Olfactory cTiamher 

 frequently extends above, and in some cases also underlies the Ehin- 

 encephalic fossae ; it always contains large and complicated turbinals. 



Digitigrada. In most Digitigrada the frontal region is convex transversely, 

 but depressed in the median line : the sagittal crest is largely developed : the 

 paroccipitals and mastoids have coalesced on each side to form a triangular plate, 

 broad and thick, and supporting the back part of the acoustic bullae. The tri- 

 angular occipital region is remarkable for the depth and boldness of the sculptur- 

 ing of its outer surface, especially in Felidse, in which the carnivorous character 

 reaches its maximum. The pterygoids are perforated by the ecto-carotids only, in 

 the Yiverridae alone, in which group also are to be found instances of the fro7ital 

 developing orbital processes, which meeting the malar, circumscribe the rim of 

 the orbit {e.g. Ichneumon Mangusta). 



Semi-plantigrada. The sagittal crest is small. There is a considerable post- 

 orbital constriction. In most Mustelidse the rhin-encephalic fossa is less distinctly 

 defined from the cranial cavity than in the Flantigrada : but in the Lutra the 

 cranial cavity is remarkable for its great posterior expansion, and its extreme 

 contraction between the rhin- and pros-encephalic divisions. 



Flantigrada. Both Paroccipitals and Mastoids are large, except in Gulo. The 

 Pterygoids are generally perforated by the ectocarotids (except in MeHdae). The 

 skidl of Meles taxus (Badger) is remarkable for the closeness with which the 

 transverse condyles of the lower jaw are grasped by the borders of the articular 

 grooves at the basec^of the zygomatic processes. 



* Marsupialia-Dasyuridae. 



t This being the case in the Plantigrade Bears that do not move by hounds, 

 and in the Pinnigrade Seals, that can only shuffle along the ground, as well as 

 in the typical Digitigrade Felidae, tends to refute the theory that the final cause 

 of these ossifications is to prevent the concussion of the several parts of the brain 

 against one another when the creature leaps or boimds. 



