^7 



where it joins the anterior bone before described. In our 

 Sydney whale this 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 equila- 

 teral 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 " ensi- 

 form portion." 



I have been fortunate in getting possession of the sternum 

 of the other sperm whale thrown ashore in Botany, as it 

 has led me to understand the structure of this part in 

 such animals, as compared with the same in dolphins. Our 

 two sperm whales may be said to have their sternum com- 

 posed 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 fore- 

 going 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 termination 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. Does the 

 sternum in the same species vary in this manner ? Is it a 

 sexual distinction ? — or am I describing two different spe- 

 cies ? Unfortunately, the Botany sperm whale was in such a 



