RORQUALS 149 



some cases due to varying conditions of maturity. 

 Thus Sir W. Flower has figured a sternum of B. 

 borealis, in which the ossified portion consisted only 

 of a roundish piece of bone, the cruciform shape of 

 the entire sternum being, however, shown in the 

 surrounding cartilaginous regions. 



^J O <-? 



As to the number of phalanges in the hand of 

 various species of Balcrnoplera, the following table 

 from Kiikenthal* gives the ascertained facts : 



B.sibbaldii I, i II, 5 III, 7 IV, 7 V, 4. 



B. borealis I, I II, 4 III, 7 IV, 7 V, 4. 



B. musculus I, i II, 4 III, 7 IV, 6 V, 4. 



B. musculus I, o II, 5 III, 6 IV, 7 V, 4. 



B. musculus I, i II, 4 III, 6 IV, 6 V, 5. 



B. rostmta I, i II, 4 III, 8 IV, 7 V, 4. 



B. rostrata I, o II, 4 III, 7 IV, 6 V, 3. 



But these tables, according to Kiikenthal, have to 

 be corrected by his discovery of a rudimentary finger 

 (Fig. 2, p. 9) lying between the third and the 

 fourth of the above enumeration. This consisted 

 in an embryo of Bal&noptera musculus of three 

 slender phalanges lying at the upper (free) end of 

 the interspace between the digits already mentioned. 

 In this case the reputed thumb will be a prepollex, 

 and the missing digit will be No. III. An obvious 

 conclusion with regard to this rudiment is to regard it 

 as a division of a digit, such as has been described in 



o ' 



the Beluga. But certain considerations derived from 

 the distribution of the nerves in the hand of this 



* Op. cit. (on p. 31). 



