— 127 --^ 



little way distant, so that the connection is not formed by an articular surface, 

 but by connective tissue. 



The third and fourth ribs conform more to the normal type of a rib, 

 and besides the arched lath of bone, display a more pronounced capitulum, 

 a costal neck and angle and a rough knobby part for the articulation with 

 the transverse process of the corresponding vertebra. Besides the shape also 

 the insertion of these ribs conforms more nearly to that in other mammals, 

 in as much as the knobby part of the costal angle is produced higher so as 

 to rest against the termination of the transverse process of the corresponding 

 vertebra. 



According to True (6) p. 185, in Balaenoptera musculus L. (the Ocean- 

 City Whale) a capitular process also occurs on the 2nd, 3rd and 4th ribs, 

 therefore unlike what is found in our case, also on the 2nd rib. 



The capitulum of the third dexter rib presents a somewhat atrophied 

 character, this capitulum being already more removed from the vertebral body 

 in the 4th. Both these features form a transition to the 5th rib, where as 

 the picture shows, the capitulum is altogether missing; at the neck of the 

 rib the apex terminates in a point, leans on nothing and indeed remains a 

 good way removed from the vertebral centrum. The upper extremity of this 

 5th rib is so noteworthy, because by comparison with the previous and 

 subsequent ribs it brings out so clearly, how the articulation of this termination 

 of the rib passes from the centrum of the vertebra to the extremity of thé 

 transverse processes, (this latter being the typical connection in the Cefacea, 

 in contradistinction to the double connection that is the normal one in Mam- 

 malia). 



This looser fitting of the ribs makes it easier for them to recede inwardly, 

 which capacity for yielding is required in diving to great depths, owing to 

 the immense pressure then brought to bear upon the body. 



In the 6th and subsequent ribs the upper articular extremity retains not 

 a trace of a capitulum or neck and is accordingly articulated only with the 

 apices of the transverse processes for which purpose articular surfaces cus- 

 hioned with cartilage are clearly available. The articular surface at the end 

 of these lateral processes then has an externo-posterior direction. 



As the ilustrations show the rib-end now bears a more or less rounded 

 character, sligtly suggesting to the observer the capitulum, though this organ 

 had already vanished in the 5th rib. Herewith we have arrived at the normal 



