yO WHALES 



passage in the Pigmy Sperm Whale, a black or nearly black species with 

 a maximum length of 13 feet, which occurs in all temperate waters, and 

 whose head is much smaller than that of the Sperm Whale (^ as com- 

 pared with ^ of the total length). The Pigmy Sperm Whale, therefore, 

 has a much smaller spermaceti case, and its head is, moreover, more 

 spherical, so that the case has a much smaller effect on the animal's centre 

 of gravity. The nostrils therefore lie right on top of the head, just as they 

 do in other whales and dolphins (Fig. 33). 



Our remarks about the position of the l)l(nv]iole in the more recent 

 Cetaceans have interrupted oiu' discussion of the Archaeocetes. In most 

 of their representatives the nostrils were neither in front of the snout, as 



Figure 32. A Fin Whale surfacing while swimming slowly, when the tip of the snout always 

 remains submerged. {Gunther, ig^g.) 



they are in terrestrial mammals, nor as far behind the snout as in modern 

 whales, but half-way between the two - another pointer that these 

 animals were not as well adapted to aquatic life as the more recent species, 

 and that they were still much closer to their terrestrial ancestors. 



\Vhile we are discussing the migration of the whale's nostrils in the 

 ccjurse of its evolution, we might also look at what has happened to the 

 l)ones of the skull during this process. For side by side with the retrogression 

 of the nostril there occurred a strong development of the jaws, making it 

 possible for them to hold the long row of uniform, sharp teeth of the 

 Odontocetes, or the great number of baleen plates of the Mysticetes. As 

 a conseciuence, not only has the nasal l^one migrated far to the rear; the 

 maxilla and pre-maxilla have been extended to overspread the l^raincase. 

 In Odontocetes, these two bones were pushed right over the frontals, 

 while the parietals became depi^essed laterally (Fig. 34). In Mysticetes, 

 the pre-maxilla and also the tip of the maxilla were pushed across the 

 frontals, while the bottom of the maxilla was pushed beneath them. The 

 whole process is known as the telescoping of the Cetacean skull. 



The Archaeocetes showed no signs of this telescoping, with the exception 

 of one of the latest representatives, the fairly short Patriocelus, a skull of 

 which was discovered in the upper Oligocene (roughly 20 million years 

 ago) deposits at Linz on the Danube. The structure of its skull strongly 

 resembled that of the Mysticetes, although Patriocelus cou\d not have been 

 a direct ancestor since, according to fossil evidence, Mysticetes had 

 already existed some seven million years earlier. The fact that Patriocelus 



