No. 473] 



SOWERBY'S WHALE 



365 



mation of the elements of right and left sides, and thns approaches 

 the condition described by Fischer ('92) for the Cap Breton 

 specimen whose sternum was likewise of four pieces. The fourth 

 was notched in front and had a central hole and a posterior notch. 

 This central hole evidently corresponds to the two notches that 

 would have been formed between the fourth and fifth sternal ele- 

 ments had they failed to fuse with each other. In the Annisquam 

 specimen this space has been quite obliterated. According to 

 A. W. Malm ('85) the sternum of the Skager Rack whale con- 

 sisted of five pieces of which the two posterior were ankylosed, 

 while that of the Vanholmen specimen was of four segments. 

 Aurivillius ('86) states that the sternum of the Bohuslan skele- 

 ton was of four pieces of which the last is practically like the others 

 save that the posterior notch is nearly closed. The sternum of 

 the Rugsund specimen as figured by Grieg (:04, p. 33) is likewise 

 of four segments, but the two elements of the fourth segment have 

 not united medially while that of the left side is ossified with 

 the next anterior piece. The 1885 Shetland whale had five sternal 

 pieces (Turner, '85) but the 1881 Shetland example had four 

 sternal pieces only, the posteriormost of which, as in the Anni- 

 squam skeleton, represented a fusion of the fourth and fifth pairs 

 of elements (Turner, '82). Still another variation is seen in the 

 Ostend specimen in which the two elements composing the fifth 

 or posteriormost piece are separate both from the piece next 

 anterior and from each other, while that of the left side is ap- 

 parently displaced so as to be in advance of the corresponding ele- 

 ment of the right side (Van Beneden, '64, pi. 3, fig. 2). An addi- 

 tional point of interest in the Annisquam sternum is its bilateral 

 asymmetry for the right-hand elenuMit of each of the four pieces 

 is slightly longer than tiiat of the left .side (Flo-. 4). Thus the 

 extreme lengths of the right-hand elements in eentiint^ters are: 15.1 ; 

 8.4; 6.0, and 7.1, while those of the k>ft-han.l elements are 14.7, 

 7.9, 5.85, and 6.8 respectively. A hke asyinnietrv is seen in 

 Grieg's figure of the Rugsund specimen. 



For convenience of reference, the known recorded specnnens 

 of Sowerby's whale are listed in the following table: — 



