HISTORY OF WHALES 



191 



i88z) and Italy (Portis, 1885). One of 

 the most complete Pliocene balaenopterine 

 skulls in existence was found in 1806 on 

 Monte Pulgnasco, Italy, in blue clay of 

 of Plaisancian age and it, Balaenoptera 

 cuvieri (Van Beneden, 1875), bears the 

 name of the famous French palaeontol- 

 ogist, Baron Georges Cuvier. 



MORPHOLOGICAL PECULIARITIES OF THE 

 MYSTICETES 



In spite of the extraordinary remodeling 

 of the skull, the mysticetes (True, 1904) 

 have retained many primitive features that 

 are no longer found in odontocetes. The 

 relations of the bones in the region of the 

 narial passages are essentially normal, and 

 the choanae lie behind the opening leading 

 to the blow holes. The proximal ethmoid 

 region and the dorsal nasal cavity are 

 completely roofed over by the nasal bones. 

 A separate lachrymal bone is retained, 

 but the lachrymal duct has disappeared. 

 The palatine is excluded from the anterior 

 wall of the narial passage. It has in- 

 creased in size and has been forced back- 

 ward, pushing the pterygoid behind it. - 

 The most extreme stage of the mysticete 

 type of telescoping is seen in Sibbaldus, 

 in which the forward overthrust of the 

 shield has carried the apex of the supra- 

 occipital to the nasal bones, and the 

 parietal sends forward a thin plate, which 

 is applied to the lateral surface of the 

 ascending process of the maxillary above 

 the abruptly depressed base of the supra- 

 orbital process. The interlocking of the 

 rostrum with the cranium is more obvious 

 than in any other balaenopterine whale. 

 In Neobalaena and Balaena the forward 

 overthrust of the supraoccipital shield has 

 gone a step further, and its apex lies 

 considerably anterior to the preorbital 

 angles of the supraorbital processes. In 

 Balaena and Eubalaena the lateral com- 

 pression of the rostrum is very conspicuous. 



A pterygoid fossa for an accessory air 

 sinus has been formed in front of the 

 inner ear. The balaenid and balaenop- 

 terine whales have a similar type of 

 scapula, with large functional acromion 

 and coracoid processes. These processes 

 are reduced to mere tubercles in the 

 scapula of Megapera. The primitive con- 

 dition of the elbow and wrist joints has 

 been lost. The carpus in Balaena is 

 immovable and broad, and conspicuously 

 lengthened in Megapfera. The lumbar 

 vertebrae are furnished with widely pro- 

 jecting transverse processes. The ribs 

 exhibit a tendency to restrict their 

 connexion with the thoracic vertebrae 

 and with the atrophied sternum, which 

 consists of the manubrium alone. The 

 ribs of living mysticetes are single- 

 headed in contrast to the normal type of 

 rib found in some of the cetotheres. 

 Considerable remnants of the hind limb 

 are retained, including the rod-like pelvis, 

 the atrophied femur, and in some cases 

 a vestige of the upper end of the tibia. 

 The caudal vertebrae acquire large centra 

 with broad flattened transverse processes 

 to conform to the manner in which the 

 tail is wielded. 



We have seen that the early cetotheres 

 lost their teeth and acquired two rows of 

 blade-like plates of baleen depending from 

 the roof of the mouth, which served as a 

 seine when the animal was feeding. 

 Small crustaceans or fish constitute the 

 food of the living whalebone whales, and 

 the cetotheres no doubt subsisted on the 

 same types of food. In the living mysti- 

 cetes the prey is engulfed in the oral 

 cavity along with a large quantity of 

 water, which necessarily must be expelled 

 by the tongue before such small prey can 

 be swallowed. Hence these plates of 

 baleen with internal marginal fringes of 

 intermatted bristle-like fibers form a 

 strainer remarkably w T ell adapted for 





