Bknham. — On the Lesser Sperm Whale. 



165 



and the least breadth, measured across last sternebra, is 

 45 mm. 



The cartilage of this and other parts of the skeleton has 

 been treated by the glycerine-gelatine method, and retains its 

 true form and relations ; but, since the cartilage is not likely 

 to be present in all skeletons, I give the measurements of the 

 bony parts as well : — 



First bony sternebra — 



Length (lower surface) ... 

 Breadth (anterior end) ... 

 Breadth (posterior end) . . . 

 Thickness (dorso-ventral) in middle 



Second bony sternebra — 

 Length 



Breadth (anterior end) ... 

 Breadth (middle) 

 Breadth (posterior end)... 

 Thickness 



Third bony sternebra — 



Right ossicle — Length ... 



Breadth 

 Left ossicle — Length 



Breadth . . . 

 Thickness 



The anterior end of the sternum is slightly bent upwards, 

 but otherwise the bones are flat, with rounded lateral margins. 

 The 1st sternebra is thinner at anterior than at posterior end. 

 The thickness increases from the anterior end of sternum 

 (where it is 8 mm.) to hinder end (13 mm.). The margin of 

 the last sternebra — or, rather, of each of the two constituent 

 ossicles — is not rounded, but slopes away from the dorsal 

 surface outwards and downwards, so that the lower surface 

 is wider than the upper (43 mm.). 



The hyoid bone is very briefly referred to by Wall, and is 

 rather more fully described by Van Beneden and Gervais, 

 who figure it. In the Purakanui specimen it was complete, 

 the bones and cartilages being uninjured. 



The basi-hyal is a flat irregularly semicircular bone, at the 

 anterior margin of which is a pair of cartilages, which evidently 

 correspond to the bony apex of the basi-hyal of Physeter, but 

 which in Cogia do not appear to ossify. The thyro-hyal bones 

 are circular discs imbedded in a large cartilaginous plate. 



The anterior cornu consists of two segments, a proximal 

 short, curved, subcylindrical cartilage (cerato-hyal) and a longer 

 distal region, in the middle of which is a cylindrical bone (the 

 stylo-hyal). 



