AQUATIC MAMMALS 



The whale has no external neck, or at least there is no constriction at 

 this point, save to a barely discernible extent in Platanista and Delphinap- 

 terus, in both of which the series of cervical vertebrae is relatively longer 

 than usual in this order. This is for the reason that the cervicals have 

 become much shortened in all Cetacea, but in some more than others, and 

 there is variation in other respects, this being best illustrated perhaps in 

 the Odontoceti. The individual vertebrae may be distinct with the cen- 

 tra either fairly thick or wafer thin, all may be fused into one bony com- 

 plex, or intermediate conditions may obtain, save that invariably, with 

 the exception of the cachalot, any fusion which occurs is first manifested 

 anteriorly. It is probable that this series is shortest in those sorts in which 

 all the elements are fused. Among odontocetes it is likely that Pla- 

 tanista has the longest neck of any genus now living, but the skeletons 

 available are disarticulated and unsatisfactory for determining this point. 

 The neck of Delphinapterus is also relatively long, as mentioned. Among 

 mysticetes the longest neck occurs in the gray whale (Rhachianectes), 

 which is famous for having this member unusually mobile, and thereby 

 hoisting whaleboats several feet above the water by a thrust of the head. 



It is difficult to determine the exact percentage of the cervical series 

 to body or even total skeletal length. The cervical length may be taken 

 with ease for the elements are either fused or were in hfe separated by an 

 insignificant amount of intervertebral substance; but this dimension is 

 almost invariably omitted from existing osteological reports, or else one 

 does not know if the intervertebral disks of the remainder of the skele- 

 ton were allowed for. In Neomeris I found that the cervical length 

 constituted about four and one-half per cent of the skeletal length, but 

 the specimens were disarticulated so that this percentage is greater than 

 is actually the case in life. From rather rough measurements of the 

 mounted baleen whales in the National Museum, having artificial in- 

 tervertebral disks of an unknown degree of error, I found that the per- 

 centage of cervical length to skeletal length was in Rhachianectes, 4.2 ; 

 Sibbaldus musculus, 3.7; Megaptera nodosa. 3.6; Balaenoptera physalus, 

 3.4; and in Eubalaena, with its fused cervicals, but 2.4. The latter figure 

 also obtains in Physeter, according to measurements furnished by Doctor 

 Stone of the specimen in the Philadelphia Academy of Sciences. 



Shortening of the cetacean neck has always awakened the liveliest in- 

 terest and has caused much speculation. The most popular belief may be 

 summed up in the words of Winge (1921) : "The head, during swim- 

 ming is held directed as firmly as possible forward. The neck is not 

 moved, and for this reason it becomes short and stiff. During motion 



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