DR. J. MUBIE ON THE WHITE-BEAKED BOTTLENOSE. 145 



consistent with the structures, obviating the narroAvness of the 

 alimeutaiy channel by the presence of the upshot larynx. 



Excepting in being moderately developed, the arytenoideus 

 posticus and lateralis present no variation. 



The hyoideus, a thick broad plane of fibres, is attached between 

 the cornua. It is tendinous anteriorly, chieiiy, however, on the 

 inner side ; and the fibres have a direction backwards and down- 

 wards : the outer ones are ranged in a difi'erent plane from those 

 of the inside, being more perpendicular. It follows from this 

 difierentiation in the planes of contraction that, as with the in- 

 tercostals, the resultant is a diagonal force. 



4. Articulation of tJie Lower Jaw. — There is no definite or 

 well-pronounced synovial membrane and sac. What may repre- 

 sent these is an intervening layer of softish fibro-elastic tissue 

 about 0-1 inch thick, which, however, is in nowise separate or 

 distinct fi'oni the general fibrous lining of the joint. I specially 

 examined the parts with the object of observing whether any 

 synovial fluid would exude on the fresh joint being cut into; 

 but although the tissues were moist, nothing which I could 

 identify as such exhibited itself. 



Between the hollow for the lodgment of the condyle and this 

 process itself there is a general lining of strong glistening fibres. 

 These, at the moveable portion, are soft and yielding. Outside 

 the joint is enwrapped, as it were, by a powerful fibrous invest- 

 ment, which partly interlaces or joins the interarticular fibres. 

 The strongest band of exterior fibres, which would appear to 

 represent the external lateral ligament of authropotomists has a 

 vertical direction or very slightly obliquely forwards and down- 

 wards. The attachment of this ligamentous bridge superiorly is 

 the junction of the squamous and jugal bones, and inferiorly the 

 anterior root of the condyle. 



The fibrous substance of the socket or glenoideum merges into 

 the temporal muscle above, and also by a continuation of fibres 

 I)asses on to the venous network lying immediately on the inner 

 side of the mandible. 



John Hunter, in his memorable " Observations on the Struc- 

 ture and Economy of Whales " *, was the first to state of the 

 groups in general that a thick ligamentous substance, with oily 

 particles in the interstices, formed the mandibular articulation, 

 a capsular ligament and double joint being absent. 

 * Phil. Trans, vol. xvi. p. 314. 



