HISTORY OF WHALES 



J 79 



shallow alveolar grooves. There is a 

 large incisure and a smaller posterior 

 foramen in each maxillary bone above the 

 orbit. 



Vastness of size is so generally associated 

 in the popular idea with the whalebone 

 whales that relatively few realize that 

 gigantic species have been developed also 

 among the toothed whales. Both giants 

 and dwarfs may appear in whales con- 

 structed along similar lines. The living 

 sperm whale, or cachalot, Pbyseter catodon, 

 is the largest known odontocete, either 

 living or extinct, and there is only one 

 described Miocene species Ontocetus oxymyc- 

 terus (Kellogg, 192.5) that approaches it 

 in the size of the skull. Comparative 

 measurements indicate that a complete 

 skull of this extinct physeteroid would 

 measure more than iz feet in length. 

 The extremity of the rostrum was formed 

 by the premaxillaries, and three large 

 teeth were implanted in each. The 

 largest mandibular teeth measure about 

 iz inches in length, and all of the teeth in 

 both jaws were lodged in distinct alveoli. 

 It should be noted, however, that the 

 alveoli were too large and the roots too 

 loosely fitted to hold the teeth in position 

 independently of a dense ligamentous 

 gum. The enamel on the crowns of these 

 teeth is ornamented with coarse longi- 

 tudinal striae. 



Physeteroids with functional teeth in 

 the upper jaws continued to near the end 

 of the Miocene, when they seem to have 

 disappeared from geological history. 

 Their remains have been found in Upper 

 Miocene deposits in Europe, North 

 America, and Japan. The incomplete 

 skull of Orycterocetus mediatlanticus (Cope, 

 1895; Kellogg, 192.5) found in the St. 

 Mary's formation at Drum Point, Mary- 

 land, has the lateral margin of the maxil- 

 lary excessively thickened at the level of 

 the orbit, but the positions of the maxil- 



lary foramina and the disposition of the 

 maxillary alveoli are similar to the Lower 

 Miocene Idiorophus. 



The number of physeteroid types (Abel, 

 1905) found in the Upper Miocene black 

 crag of the Antwerp basin, Belgium, is 

 truly surprising in view of their scarcity 

 in later geological formations. The 

 distinguished Austrian palaeontologist, 

 Professor O. Abel has recognized a rather 

 large number of physeteroids in these 

 deposits, including Scaldicetus morte%elensis , 

 Physetenda dubusii, Thalassocetus antiverp- 

 iensis, Placo%iphius duboisii, and Prophyseter 

 dolloi. The skulls of these extinct Belgian 

 physeteroids differ from one another in 

 certain details of cranial construction, but 

 all possess the large supracranial basin. 

 The largest of these is Physetenda dubusii, 

 whose skull measures less than six feet 

 in length; each mandibular ramus is 

 furnished with zo teeth about 5 inches 

 long, of which iz are restricted to the 

 symphysis. No enamel is present on the 

 crowns of these teeth. The other species 

 have somewhat smaller skulls, those of 

 Scaldicetus morteZ.elensis and Placoxiphius 

 duboisii being less than 3 feet in length. 

 In Placo^iphius the upper teeth seem to 

 have been completely lost, for the alveolar 

 grooves are nearly closed. Scaldicetus 

 on the other hand is said to have retained 

 the maxillary and premaxillary teeth, and 

 the unworn teeth of this physeteroid have 

 the crowns covered with longitudinally 

 striated enamel, in addition to vestigial 

 crenelated cutting edges. The roots of 

 these teeth are simple and have a rather 

 large pulp cavity. 



The culmination of the tendency toward 

 the abnormal development of a spermaceti 

 cushion may be observed in the living 

 genus Pbyseter, the great size of whose 

 skull is disproportionate, in respect both 

 to the brain and to the body. In this 

 genus, the spermaceti cushion has attained 



