478 SCHULTE, SEI WHALE. 



laterad and rostrad to articulate with the zygoma and postorbital process of the frontal; the 

 more slender postglenoid process is directed ventrad and caudad and gives attachment to the 

 dense fibrous envelope of the auditory meatus as well as to the capsule and fibro-cartilage of 

 the temporo-maxillary joint; mesad and rostrad a narrow plate, the ventral surface of the 

 squama, extends to the external pterygoid and represents the glenoid region. In the line of 

 union is situated the foramen ovale. This is bounded mesad by a process of the squamosal, 

 which overlies the pointed caudal extremity of the external pterygoid. It is the processus 

 falciformis of Beauregard, and in this foetus is broad and very short in comparison to its pro- 

 portions in his adult of B. musculus ( = physalus). The angle between this process and the post- 

 glenoid is filled with dense fibrous tissue through which Meckel's cartilage makes its way to the 

 tympanum. Rostrad the glenoid region is separated from the squama by a ridge, which sweeps 

 laterad to the ental surface of the zygomatic process, and here becoming more prominent affords 

 a very definite boundary between the temporal and zygomatic fossae; thus corresponding to 

 the anterior root of the zygoma and the beginning of the infratemporal crest. 



Of the elements of the basicranial axis only the basi-occipital is exposed, the basisphenoid 

 being covered by the expanded alae of the vomer and their articulations with the vaginal pro- 

 cesses. The basi-occipital is, relative to that of the adult, very long. It lies in a deep depression 

 between the auditory bullae, and on each side sends ventrad, a low falcate process to which the 

 fibrous wall of the bullae is attached. These ridges serve also for the insertion of the rectus- 

 scalene tendon. Rostrad they become lower but can be followed to the vaginal processes. Here 

 laterally placed and partially overlapped by the vaginal process is the ectal orifice of the canal 

 in the basisphenoid for the internal carotid artery. The exoccipitals extend caudad of the bullae 

 to the exposed bases of the otic capsules, which appear between them and the squamosals, here 

 articulating with the hyoid bars, and on their caudomesal aspects giving passage to the facial 

 nerves. Between the exoccipital and the bulla, is the large posterior lacerated foramen which 

 is divided by membrane into two compartments, a mesal one for the IX-XII nerves, and a lateral 

 one for the jugular vein. 



The enormous auditory bulla occupies the region between the external pterygoid, the squa- 

 mosal, the basi- and ex-occipital. Laterad it is prolonged into the external auditory meatus 

 which is directed to the notch in the squamosal dorsal to its postglenoid process. Its wall is 

 composed of extremely thick lamellated connective tissue, which is attached mesad and caudad 

 to the vaginal process and occipital, rostrad and laterad to the external pterygoid, squamosal, 

 and otic capsule, and is prolonged upon the floor of the auditory meatus. In this fibrous capsule 

 is embedded the tympanic, which is relatively of small size and irregularly crescentic in form. 

 It sends two cornua laterad. Of these the caudal is far the longer and extends to the base of 

 the otic capsule, to which it is loosely attached by connective tissue. The rostral cornu is situated 

 caudal to Meckel's cartilage, where it ends without other than membranous attachment to 

 adjacent structures. Save at one point the tympanic is then isolated from other bones, and 

 constitutes at this time a small plate in the extensive fibrous wall of the bulla. The size of 

 the auditory bulla makes it the dominant feature of this region of the skull, and joined to the 

 small development of the squamosal, and the relatively long basi-occipital, renders the basis 

 cranii at this stage of development exceedingly dissimilar from that of the adult. 



Norma lateralis. The high convexity of the cranium, the concavity at its junction with 

 the rostrum, the horizontal base-line, together with the less prominent orbital margin and zygo- 



