134 PROFESSOR STRUTHERS. 



inch in length. The whole of this sloping end, 5 inches, 

 has been covered by cartilage, as all the ends behind this 

 have been. The third rib has rather more slope than the 

 second. 



The extent to which the lower part of the ends project in- 

 wards beyond the upper part at the tubercle is seen in the sixth 

 column of the Table. It continues to be about 2 inches back to 

 the 12th. The 2nd and 3rd ribs cannot be said to have a beak 

 in the sense that these two ribs have in B. musculus, or even as 

 the 4th of B. musculus has. After the 7th the slope is greater 

 in Megaptera than in B. musculus, as seen in the Table. The 

 remark of Van Beneden and Gervais that " la troisieme surtout 

 et la quatrieme different des autres par une tete distincte " {op. 

 cit, p. 127) does not apply to this Megaptera. 



Although, as seen in the end view, the articular ends of the 

 ribs are directed less downwards and backwards than in B. 

 musculus, the terminal torsion, affecting the inner half of the 

 external neck and the end proper, is very marked. The twist 

 back of the lower part of the articular end is well seen when 

 the series of ribs are laid with the posterior surface upwards. 

 On the first four there is both bending back of the inner part 

 of the external neck and twisting back of its lower edge. From 

 the 5th to the 8th there is only the decided twist ; on the next 

 two less twist ; and on the last four more. The twist back of the 

 lowest part of the articular end in some (4th to 7th on right 

 side, 4th and 5th on left side) runs on to a projection like the 

 end of a finger. This projection is marked on the left 5th and 

 7th, I to f inch long ; on the 5th it is like the end of a thumb ; 

 on the 7th like the end of a little finger. This projecting cone 

 is not seen in the front view of the rib, and has not been 

 covered by cartilage. It may be regarded as a rudimentary 

 beak, but it is irregular and not symmetrical. 



Adaptation of the Ribs to the Fossce on the Transverse Pro- 

 cesses. — The distinction of the articular end of a typical rib into 

 upper and lower parts is more marked in Megaptera than in B. 

 musculus. The whole area is more bent, almost kidney-shaped. 

 The concavity, going on the surface from the most concave part 

 of the posterior margin, marks off about the upper J-. This 



