ON THE GREENLAND RIGHT- WHALE. 119 



lines from the above-mentioned thin division, abeady completely calcified, and composed entirely 

 of osseous fibres arranged in layers ; and even in that most distal, not yet ossified small 

 portion, it had a similar fibrous appearance, though here it was not observed to contain any 

 earthy matter. The part of the sternal rib (e) adjoining the thin membranous partition was quite 

 similar to this soft innermost extremity of the vertebral rib ; but the sternal rib itself {d) was a 

 perfectly compact and uniformly diaphanous genuine cartilage without the least trace of any 

 inserted fibrous tissue. 



After having found the sternal ribs of the first pair of ribs attached to the sternum, our 

 next object was to discover whether any trace of them might be found also in the suc- 

 ceeding pairs of ribs. Our examination of the same foetal skeleton gave us an affirmative answer 

 to this question, as may be observed from the woodcut, page 118, as far as the second rib was 

 concerned ; in this figure, b', c', d', and e' have the same signification as to this rib, as b, c, d, 

 and e have to the former. Li the succeeding ribs a similar trace of sternal ribs was scarcely 

 perceptible. 



The sternum of the Greenland whale, like that of all the rorquals, serves, as we have stated 

 just now, as an attachment to the first pair of ribs. Only one question might still arise as to the 

 relative position of the sternum and the ribs, namely, whether a rudimentary prolongation might 

 not perhaps issue from the hindmost extremity of the sternum in the mesial Hne for the 

 attachment of the succeeding ribs ; but this supposition was found, on a careful examination of 

 our foetus, to be without any foundation. For those pairs of ribs immediaitely succeeding the 

 first approach pretty nearly to the mesial line of the ventral surface, and in this line we only 

 found a slight fibrous tissue corresponding to the so-called linea alba, but this fibrous tissue did 

 neither contain any trace of cartilage nor was it in any close connection with the periosteal 

 membrane of the ribs, or that of the sternum. 



As to the shape of the sternum of the Greenland whale, we must on the whole refer 

 our readers to our illustrations of those of the foetus and the half-grown individual. In our 

 larger skeletons, however, the sternum had not exactly the same form, and some other 

 examples which we have had for our examination have again proved different. They all agree in 

 the following points. The external surface, which looks forwards and downwards, is flat in the 

 longitudinal direction, but convex transversely, the internal surface looking backwards and 

 upwards is convex longitudinally and concave transversely ; the sternum has its greatest breadth 

 anteriorly, especially before the attachment of the ribs ; behind it runs out into an obtuse point. 

 The lateral margins are in the middle, or a httle in front of this, very much thickened, by which 

 the attachment of the ribs is indicated; and posteriorly they become gradually thinner. But 

 the anterior margin is sometimes somewhat convex, as in that of our twenty-two feet long skeleton 

 (Plate II, fig. 3) ; sometimes, on the contrary, having a greater or smaller notch in the middle. 

 The length of the sternum is always somewhat greater than its breadth ; in that of our forty -four 

 and a half feet long skeleton the former is twenty inches, the latter nineteen inches ; in another 

 one the length is twenty-four, the breadth nineteen inches ; in a third the length twenty-three, 

 the breadth sixteen and a half inches. 



