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bone before described. lu our Sydney whale tliis second piece 

 of the sternum is composed of two distinct triangular bones joined 

 together by cartilage ; and which, if consolidated into one, would 

 make an equilateral triangle, having its point directed towards 

 the tail of the animal. These bones, in the Yorkshire whale, are 

 consolidated into one flat irregular piece, and Beale describes a 

 third piece which expands very much, and also a small ensiform 

 portion. This last alone would show his animal to be a distinct 

 form of sperm whale. The bottle-nosed dolphin has also a third 

 bone, but Cuvier makes no mention of its having any " ensiform 

 portion." 



I have been fortunate in getting possession of the sternum of 

 the other sperm whale thrown ashore at Botany, as it has led me 

 to understand the structure of this part in such animals, as com- 

 pared with the same in dolphins. Our two sperm whales may be 

 said to have their sternum composed of six bones, three on each 

 side of a cartilaginous medial symphysis. The first two form by 

 their junction that anterior bone of the dolphins, so remarkable 

 in some species for its medial perforation. But in the Botany 

 sperm whale, each of these first two is ossified with the following 

 two, which, when joined by cartilage, answer to the second bone 

 of the sternum in Delphinus Tursio. The third two bones of the 

 cachalots answer to the third bone of dolphins, but in our Sydney 

 sperm whale these last are ossified with the foregoing two ; so 

 that we may say, that of the three bones on either side of the 

 sternum, the Sydney whale has the two last anchylosed together, 

 and the Botany whale the two first bones. Besides, the termina- 

 tion of the sternum is widely different in these two individuals. 

 In our Sydney skeleton the two last bones converge to a point, 

 whereas in the Botany specimen they diverge from each other 

 with truncated summits, thinned off towards their inner edge. 

 Docs the sternum in the same species vary in this manner ? Is 

 it a sexual distinction ? — or am I describing tw^o different species ? 

 Unfortunately, the Botany sperm whale was in such a state of 

 decomposition when I saw it, and besides had been so much cut 

 up, that I must confess it to be out of my power to determine 



