Measurement of ribB. 



55 



Balaenoptera Rostrata. 



First rib. Lower extremity widest then the rib gradually dimi- 

 nishes. 



Second rih. The lower end is narrower than the part imraediatel) 

 above. 



Third rih is narrow at the end. It becomes broad as it is traced 

 upwards and becomes narrow again at the upper part. 



Fourth rih broad in the lower third except at the end. 5*^ Broad 

 lower third, narrower in the middle, broader above. 6* Wide at the 

 junction of the middle and inferior third. 7*'' Broad at the junction 

 of the middle and lower fourth. The others are broad at the junction 

 of the lower fourth with the next. 



The upper show also a great increase in breadth, in all except the 

 first five and the last. 



The fifth is more uniform. 



Manatus Australis. 





1 i 2 



t 



3 



4 5 



i 



6 



7 



8 



9 



10 



11 



12 



13 



14 



15 



16 







17 



A 



170 



220 



270 



355 



350 



380 



400 



410 



400 



40O 



400 



400 



380 



350 



370 



330 



260 



C 



15 



10 



10 



9 



9 



7 



10 



12 



12 



11 



10 



10 



10 



10 



10 



10 



9 



D 

 £ 



f 



Ol 



to CO 



O Co 



to 



KO 



! 



36 



30 



! 



o 

 30 



40 

 35 



40 

 35 



38 

 33 



42 

 35 



42 

 35 



44 

 32 



40 

 27 



47 

 30 



30 



20 



20 

 17 



F 



150 



180 



230 



260 



260 



290 



280 



240 



240 



250 



240 



230 



230 



200 



210 



180 



230 



D = Radial by tangential breadths. 



E = approximate breadtlis at the angles. 



F = Oiätance of the broadest part from the lower end. 



The depth of the thorax is 99 mm., the ribs have large tangential 

 diameters in proportion to the radial diameters except in the anterior 

 three. The fourth rib widens above and the increased tangential 

 diameter extends farther downwards in each succeeding rib until the 

 last is reached. The angles given in the tables are the posterior 

 angles. 



