62 PROFESSOR STRUTHERS. 



Number of the Vertebrae. Megaptera has the same number 

 of dorsal vertebrae as B. borealis and one less than B. 

 musculus, but the striking difference is in the lumbar region, 

 Megaptera having only 10, while B. borealis has 14, and B. 

 musculus 15. This gives great shortness to the abdominal 

 region in Megaptera. The caudal region is long compared 

 with that region in B. musculus and in B. borealis in proportion 

 to the total length. The 13 feet of caudal region in Megaptera 

 against 11 feet in B. borealis, while both have 21 caudal 

 vertebrae, is not owing to greater length of the bones in 

 Megaptera but to the great length of the intervertebral fibro- 

 cartilages in Megaptera. The contrast between Megaptera and 

 the other two finners in this respect, seen in dissection, was 

 apparent also in the dorsal and lumbar regions, but was striking 

 in the caudal region. Megaptera is thus characterised by a 

 short " trunk " and a long, robust, and flexible tail, surmounted 

 by a large tail fin. These proportions of the vertebral column 

 are taken from the three articulated columns placed beside each 

 other, the proportions carefully assigned in articulation. 



Number of Caudal Vertebrae. The precise number of the 

 caudal vertebrae must often remain uncertain. In this 50-feet- 



* 



long B. musculus, what would have come out of the maceration 

 trough as the last vertebra is about 1 inch broad and \ inch 

 long. But behind it is a conical cartilage, \ inch long in the 

 now dried condition, and on the upper aspect of this, at its 

 middle, is a rounded bony nucleus only \ inch in diameter. 

 What is present as the last caudal vertebra in this Megaptera 

 is a piece of bone about the size of a commcn nut compressed 

 into a somewhat cubical form (f inch broad, \ inch in height 

 and length, but part of the length is evidently broken off). 

 There may have been a cartilage behind it as in this B. 

 musculus, and still more so in this B. borealis, the last vertebra 

 of which present is 1J inch broad, f inch long, and | inch high. 

 There can be absolute certainty only when the very end has 



far as comparison is of interest. As this is sufficient to bring out the characters 

 of Megaptera, only occasional references are made to B. borealis. The com- 

 parison which I at the same time made between B. musculus and B. borealis was 

 interesting, as bringing out numerous differences between these two species, but 

 this subject I must reserve for some future communication. The parts relating 

 to B. musculus are placed within brackets [ ] for facility of reference. 



