19 



composed of three bones — two lateral, which are the styloi- 

 deans ; and a central one, which is the true os hyoideSf and 

 which is often separable into three. The styloideans, or 

 styloid processes, are attached by a cartilage to that lobe of 

 the occipital which represents the mastoid process. The 

 OS hyoides itself has somewhat of a crescent form, having at 

 the convex and anterior part two apophyses by which it is 

 suspended by cartilages to the styloideans. On each side, 

 more particularly in young specimens, the two horns of the 

 crescent are separated by a suture from the centre piece. In 

 our Sydney whale, which is comparatively a young specimen, 

 the central bone of the os hyoides is heart-shaped, with the 

 point of the heart notched, so as to give off the two short 

 apophyses to which the styloideans are attached by cartilage. 

 It is also keeled in the middle behind, and concave within. 

 On each side we see a flat oval bone, joined by a suture 

 to this middle bone. In some Cetacea, these bones, which 

 form the horns of the crescent, are said always to remain in 

 the state of cartilage. The styloideans, in our whale, are in- 

 sulated slender prismatic bones, somewhat rounded at the 

 points. Cuvier has figured an os hyoides (O.F. pi. 226. fig. 

 15,) very like to the one just described, and which he sup- 

 poses to have belonged to the Audierne Cachalot. The 

 dimensions of the os hyoides, in our specimen, are as 

 follows : — 



Middle length of middle piece . . . . 



Greatest breadth of ditto 



Breadth of ditto between the horns 

 Length of a horn of the crescent . . 



Greatest breadth of ditto 



Length of a styloidean , 



Greatest diameter of ditto 



