ANATOMY OF MEGAPTERA LONGIMANA. 131 



back at its broad lower end, gives the last rib, of the right side, 



the appearance of having a short fourth bend on its lower six 



inches. The left 14th rib has not this, and the middle of its 



three curves is less pronounced than the corresponding curve on 



the right. 



[The 15tli rib of my 64-feet-long B. inusculus (72 inches long) 

 shows the three curves on a great scale. There was a 16th pair of 

 ribs in that B. musculus (this Journal, 1871, p. 115) loose in the 

 flesh (right 30 inches, left 22 inches long), which the 15th, the 

 last, of tliis 50-feet-long B. musculus closely resembles, except that 

 the latter has more of the sigmoid form. The upper 9 inches taper, 

 the upper 6 inches rounded, to a point half the size of the end of the 

 little finger.] 



36. Vertebral Ends of the Ribs. — The modifications of 



these in Megaptera will be better understood after observing 



them in B. musculus. 



[In B. musculus. — The 1st rib of this B. musculus has no beak.^ 

 The 2nd and 3rd ribs have a long capitular process or beak. This 

 process, and the ligament which prolongs it to the body of the 

 vertebra in front, together represent the neck and head of the com- 

 plete rib of the toothed Cetacea and of most mammals. Above the 

 base of the beak is the well-marked tubercle by which the rib arti- 

 culates with the transverse process of its vertebra, and between this 

 and the angle is the moderate constriction which may be termed the 

 external neck. The common error of calling the end of the ordinary 

 or beakless ribs of the whalebone whales the "head," and the con- 

 striction external to it the " neck," was emphatically remarked on 

 long ago by Eschricht (loc. cit., p. 137). The rapid shortening of 

 the capitular process after the 3rd gives the ribs first a sloping and 

 then a rounded end. The 4th shows a considerable slope to a sharp 

 point ; after the 4th there is less and less slope, and the angle below 

 is rounded off, so that the most projecting part of the end is not its 



^ In my 60|-feet-loiig B. musculus the 1st pair of ribs have as well-marked 

 and as long a beak as the 2nd pair have (this Journal, 1872, p. 47). In my 

 64-feet-long B. musculus the beak occurred on the left side as a separate piece, 

 articulated by cartilage to the lower part of the broad end (this Journal, 1871, 

 p. 116, and fig. 4, Plate VII.). The condition on the right side could not be 

 ascertained. In this 50-feet-long B. musculus, the end of the 1st rib is broad 

 and rounded, the lowest part, from which a beak would have proceeded, some- 

 what rounded off below and thin, and without any appearance of a movable 

 beak having existed. The cartilage- covered surface extends over the whole 

 height and breadth of the end : height 5f inches ; breadth above, 1| inch, at 

 middle | inch, at lower part \ inch. Upper f convex backwards, lower | con- 

 cave backwards. The occurrence of a beak on the 1st rib in B. musculus appears 

 to be a matter of ossification or of variation. 



