— 114 — 



In True (6) pi. 41 fig. 1, 2, 3 and 4 we can further see in the case of 

 Megaptera versabilis Cope (at any rate also a fin-whale) the extraordinary 

 width of the lower jaw, the two bony posterior extremities of which arch 

 considerably outwards, a thing which would of course be impossible if these 

 extremities were restrained by a strong articular ligament. An articulation 

 capsule is not present here, so that we can no longer speak of an articulation. 



In the description of Balaenoptera rostrata Fabr. in Carte and Macalister 

 (3) it is stated with reference to the joint of the inferior maxilla (p. 212) that 

 Hunter found no synovial bursa but that a double synovial bursa was demon- 

 strated in Balaena mysticetus L. by Eschricht and Reichhardt; but this creature 

 is not a fin-fish but a right (unfluted) whale, whose posterior extremity of 

 the lower jaw is quite differently shaped from what it is in Balaenopteridae. 

 This double synovial capsule is apparently meant to serve as an argument 

 for presuming the existence of a lower-jaw joint in Balaenoptera. Meanwhile 

 the position and relation of the lower maxilla to the skull is now perfectly 

 determined, since we know the length of the part that is produced before the 

 upper jaw and also the width of the lower jaws, whilst the falling away of 

 the lip near the corner of the mouth marks the place of the processus coro- 

 noideus. 



The sketch on page 108 shows how far removed is the so-called articular 

 process of the inferior maxilla (c) from the lower extremity of the skull (squa- 

 mosum, dj. 



This squamosum in the Buitenzorg Balaenoptera having a strong back- 

 ward deviation, unlike the downward direction in other species, it follows that 

 the distance must here be greater than m other representatives of the group. 



Some photographic reproductions of Balaenoptera musculus L. and Balae- 

 noptera physalus L. show however, that in some cases the loweh jaw is little, 

 if at all, produced forward. See True pi. 15 fig. 3 and other illustrations. 



From the preceeding we must conclude that the lower jaw possesses a 

 great mobility in the forward-backward (horizontal) direction, for originally 

 we calculated the length of the part of the lower jaw that can be produced 

 before the upper one, to be 68.2 c.M. 



We find therefore that the lower jaw can certainly be moved forwards 

 and backwards for a distance of at least '/2 ^» ^"^ ^s the condyles of the 

 jaw can consequently also be displaced more than ^4 ^> i^ is not possible 

 to assume an articulation properly so called. 



