THE WHALEBONE WHALES OF THE WESTERN NORTH ATLANTIC. 



257 



assigned to it hy Gasco, he expresses the opinion that there may originally have 

 been 14 pairs. 



In the majority of specimens the first rib is single-headed, but in the Guetaria 

 (Spain) skeleton, that of the right side shows a small secondary process adjacent 

 to the proximal end. The bifurcation is also found in the San Sebastian skeleton 

 of 1854. Gasco's description of the first pair of ribs in tliis specimen is as follows : 



"No doubt the first pair of iil)s of the young wliale of San Sebastian, placed 

 opposite the corresponding parts of the Taranto whale, exhibit certain singular 

 differences, which though they do not surprise us at present, led J. E. Gray to 

 create the genus Ilunterhis, a genus whicli no one now accepts. The superior or 

 vertebi-al extremity of the first pair of ribs is bifurcated. In the right one the 

 bifurcation extends 55 mm., but in the left does not surpass 15 mm. In the left, 

 the part of the rib which thus separates, 15 mm. long, terminates acutely and may 

 be compared to a little horn, wliich has the apex distant scai'cel}' 2 cm. from the 

 internal bolder of the rest of the rib, and about 7 cm. from its superior extremity. 

 Its circumference is 45 mm., and at the apex, 25 mm. On the other hand, on the 

 right the portion of the rib which is separate is 55 mm. long. It is somewliat 

 thicker, the termination obtuse, and it is distant its whole length only 3 or 4 mm. 

 from the inner margin of the rest of the rib. So it may even be suspected that in 

 the progress of time this portion might be completely fused with tlie rest of the 

 rib. Its apex is distant from the superior extremity of the rib only 2 cm. Its 

 circumference at the base is 8 cm., and 9 cm. near the apex. All these relative 

 differences in the degree of bifurcation in the same individual indicate clearly how 

 little of importance there is in the separation of a portion of the rib." ' 



The distal ends of the two ribs constituting the first pair are commonly unequal 

 in breadth. In the different specimens the measurements ai-e as follows: 



BA-L^NA GLACIALIS BONNATERRE. E0ROPEAX AXD AMERICAN. BREADTH OF FIRST RIB. 



The length of the first rib in a straight line is as follows : 

 'Anuul. Mus. Civic. Geneva, 14, 1879, I'P- 606, 607. ' Type of B. cisarctica. 



