COMMON FINBACK WHALE. 187 



is at nearly a right angle to this. The front edge of this great bony plate slopes forward and 

 inward forming an obtuse angle with the outer edge. The occipital bone is also somewhat 

 characteristic. Its greatest length forms about 40 percent of the total length of the skull. 

 At the vertex of the skull its sides are nearly parallel, or only slightly divergent, then spread 

 laterally to form the posterior wall of the cranium. A well marked ridge is present in the 

 middle line of the occipital. The shape of the nasals varies slightly, but as seen from above, 

 they are usually deeply notched, and the median edges approximated to form a sharp point. 

 A narrow prolongation of the intermaxillary reaches to about the middle of the nasals, and a 

 larger process of the maxillary extends upward, expanding slightly, to abut against the vertex 

 of the occipital. There is much individual variation in the shape and proportions of the vari- 

 ous bones, and it is not yet clear how much of this is due to age. The lower jaw has a promi- 

 nent coronoid process, which is lacking in the Right Whales. 



In the following table of skull measurements those in the first and second columns are 

 the dimensions (in English inches and mm. respectively) given by Dwight (1872) for the skull 

 from Gloucester, Mass., in the Society's Museum, and in the third column these same dimen- 

 sions expressed in percentages of the total length of the skull. The percentages in the fourth 

 and fifth columns are those given in True's (1904) monograph for two specimens from Cape 

 Cod in the U. S. National Museum. All three specimens are immature, and it is unfortunate 

 that no measurements of a fully adult American specimen are available. 



The percentages for the important measurements of these three skulls show a relatively 

 close agreement, and indicate to some degree the range of individual variation. 



The hyoid bones are large and somewhat inflated in outline. The form is rather charac- 

 teristic in the genus. The basihyal is flattened and has usually a deep notch at its posterior 

 end on either side of which articulates one of the stylohyals. Fused with the basihyal are the 

 thyrohyals, which are flattened, and curve only slightly upward. The two sutures between 

 these three component parts are usually indicated even in adult specimens. In the Society's^ 

 specimen, the basihyal was 4.75 in the median line, while the distance between the tips of 

 the thyrohyals in a straight line was 24.5 inches. The stylohyals were each about 15 inches 



long. 



The total number of vertebrae in the Society's specimen is 63, which appears to be 

 the maximum number yet recorded. Since unusual care was taken in the preservation of 

 the small terminal bones, it is probable that this number is correct for the specimen. The 

 formula is: 7 cervicals, 15 (or possibly 16) dorsals, 15 (or perhaps 14) lumbars, 26 caudals 

 = 03. In the Society's skeleton the 15th pair of ribs is so long as to presuppose that there 

 may have been an additional shorter pair of floating ribs, that became lost in the course of 

 preparation. In this case the total number of dorsals would be 16, as in a skeleton from New- 

 foundland recorded by True. Skeletons with 14 and 15 rib-bearing vertebrae are usual. 



