ME. W. H. FLOWER ON THE OSTEOLOGY OF THE SPERM-WHALE. 



551 



obviously incomplete ; the former has only eleven, and the latter ten. Those that are 

 present differ very notably in form and dimensions both from each other, and from 

 those of the Tasmanian skeleton ; but this is the most unsatisfactory part of the whole 

 examination, owing to the imperfection of the materials and the difficulty, in incomplete 

 sets, of ascertaining with precision which are the corresponding bones. 



Bibs. 



The ribs, though tolerably long, are (with the exception of the first) slender and light 

 for the size of the animal, at least when compared with those of a Balcena of correspond- 

 ing magnitude. This character is best illustrated by stating that in the skeleton of the 

 nearly adult Balcena mysticetus, in the Mus. of Eoy. Coll. of Surgeons, 46' in length, 

 the twelve pairs of ribs weighed 7 cwt. 60 lbs. ; in the Cachalot, several feet longer 

 and of corresponding age, the eleven pairs weigh less than 3 cwt. Nevertheless their 

 tissue is dense and compact. 



It is stated by Wall that the ribs of the left side are of larger dimensions than the 

 corresponding ones of the right. In order to ascertain whether there is a similar want 

 of symmetry in the specimen under consideration, I weighed all the ribs; and the 

 result shows considerable individual differences in corresponding ribs, and a very trifling 

 general preponderance of the left side over the right — the total weight of the ribs of 

 the right side being 16-3 lbs. 9^ oz., and those of the left side 164 lbs. 5^oz. 



Weight and Measurements of the Eibs (excluding the rudimentary eleventh pair). 



* Taken by standing the rib with its two ends on the floor, and measuring from the latter to the interior of 

 the highest part of the arch. 



3c2 



