332 Richard Owen, Esq., on Comparative Osteology. 



classification of this order. Its Osteology. Constancy in the num- 

 ber of the " true vertebra?." Extreme variety in that of the 

 " false vertebrae." Peculiarities of atlas and dentata. Cervical 

 spines of Opossum. Tail, modified to serve as a hand in the Opossums, 

 as a foot in the Kangaroos, as a balancer in the Petaurists, and a rud- 

 der in the Thylacines. Composition and modifications of the skull : 

 small cranium : long separation of the elements of the occipital and 

 temporal bones. Vacuities in the osseous palate. Inflected angle of 

 the jaw. Great diversity in the thickness of the cranial bones of dif- 

 ferent species. Scapular arch and bones of the fore-limb. Humerus 

 generally perforated at the inner condyle, and sometimes between 

 the condyles. Bones of fore-arm freely rotate in all. Scapho- 

 lunar bone of Wombat and Kangaroo. Pelvis and marsupial bones. 

 Bones of the hind-limb ; their close correspondence with those of 

 the fore-limb, in some species ; degradation of the toes in others. 

 Fossil Marsupials of Australia. Antiquity of the Marsupial type 

 upon the earth. 



Lecture xiv. — Cetacea. — Their general characters compared 

 with that of fishes ; Vertebral column : anchylosis confined to the 

 region of the neck. No sacrum. Peculiarities of ribs and sternum. 

 The skull : singular development of the cranial and facial bones : 

 their modifications in relation to locomotion in water and respiration 

 of air. The hyoid arch. The bones of the fore-limb modified as a 

 fin. Rudimental pelvic bones. Cranial and Vertebral character- 

 istics of SiRENiA. Antiquity of the true Cetacea on the globe. The 

 great Zeuglodon of Alabama. Fossil remains of Whales in the 

 Suffolk crag : their unexpected value in agriculture. 



Lectures xv. and xvi. — Ungulata, or hoofed Quadrupeds, — 

 General characters of this great natural group of Mammalia. Den- 

 tal and osteological characters of the earliest forms introduced into 

 this planet. Anoplotherium and Palaeotherium, the types of the 

 two natural primary divisions of Ungulata, viz., Artiodactyla and 

 Perissodactyla. 



Ruminant Artiodactyles. — Their osteology ; peculiarities of cer- 

 vical vertebrae. Structure of the skull : forms, structure, and growth 

 of permanent and deciduous horns. Shedding and renewal of ant- 

 lers. Modifications of the organs of locomotion. Recent introduc- 

 tion of the Ruminant type upon the earth. 



Non-ruminant Artiodactyles, represented at the present day by 

 the Hog-tribe and the Hippopotamus. Dorsal spines of the wild 

 boar. Massive skeleton of the Hippopotamus ; enormous facial part 

 of the skull as compared with the cranium. Transition to Non- 

 ruminants made by the Anoplotherium which retained many of the 

 foetal characters of the Ruminant. 



Penssodactyla ; three natural divisions of this group typified by 

 the Horse, the Rhinoceros, and the Elephant. Leading peculiari- 

 ties of their skeletons. Degradation of the feet from the pentadactyle 



