VII.] 



SIRENIA. 



101 



In the Lesser Fin Whale (/?. rostratd) the sternum is 

 cross-shaped (Fig. 40), the first ribs being attached behind 

 the Literal arms of the cross. 



FlG. 41 Sternum of Rudolphi's Whale (RaJtrnafltra A.'rra/is). showing its relation 

 l'i the inferior extremities uf the first pair of ribs. From " Proceedings Zoological 

 Society. 1883." 



In the SIKKNIA the sternum is a simple, flattened, some- 

 what elongated bone, which in the adult shows no trace of 

 segmentation. 



FIG. 42. Sternum of a young Dugong (Halicore indicia), \. From a specimen in 

 the Leydcn Museum. 



In a young Dugong (Ilalicore), Fig. 42, there are two 

 distinct ossifications, a presternum (/j), to which the first 



