Richard Owen, Esq., on Comparative Osteology. 333 



to the monodactylo structure. Determination of the bones of the 

 feet and of the retained digits. Former abundance and wide geo- 

 graphical range of the Proboscidian Pachyderms, The Elasmothe- 

 rium, Dinotherium, Macrauchenia, and Nesodon. 



Lecture xvii. — Edentata or Bruta. — Transition to this order 

 from the Ungulata made by the extinct Megatheriod quadrupeds, 

 which had both '* hoofs" and " claws ;" claws of great length in all 

 the order: teeth, if present, without enamel; few other common 

 characters. Leading divisions of the group typified by the Sloth, 

 the Anteater, and the Armadillo. Their osteology compared : nu- 

 merous dorsal vertebrae of the Unau ; numerous sacral vertebra) of 

 the Armadillo. Extreme flexibility and unusual number of vertebrae 

 of the n^ck of the Sloth. Short and anchylosed cervicals of the 

 Armadillo. Complex dorsal and lumbar vertebrae of Armadillos and 

 Anteaters. Tail very long and prehensile in certain Anteaters : very 

 short or wanting in the Sloths : of great size and strength, serving 

 as an accessory hind-limb, in the Megatherioids. Its singular armour 

 in the Glyptodons. Variable and inconstant bones of the skull illus- 

 trated by the conditions of the zygomatic arch in the Edentata. Long 

 and edentulous jaws of the true Anteaters. Modifications of the 

 fore and hind limbs for climbing, for digging, for uprooting, and 

 pulling down trees. Dermal skeleton of the Manis and of the exist- 

 ing and extinct Armadillos. 



Lectures xviii. and xix. — Bodentia. — Their numbers, exten- 

 sive distribution, feeble and defenceless character and great fertility. 

 Subdivided according to the rooted or rootless character of their 

 molar teeth, which govern the nature of their food. Their osteology 

 illustrated by the skeletons of the Squirrel, Beaver, Cavy, Jerbor, 

 and Hare. Modification of the masseter muscle and of the man- 

 dibular articulation in relation to the gnawing powers of the order. 



Insectivora. — Principal forms and osteological characters of this 

 order illustrated by the skeletons of the Hedgehog, the Shrew,- and 

 the Mole. Modifications of trunk-vertebrae in the Hedgehog, of the 

 cervical vertebrae in the Mole. Feeble or incomplete zygomatic 

 arch ; clavicles constant in the Insectivora. Relations of the ster- 

 num, clavicles, and massive fore-limbs, of the small and open pelvis, 

 and feeble hind-limbs of the Mole to its subterraneous existence. 

 High antiquity of the Insectivorous Mammalia. 



Cheiroptera. — The characters of the types of the order show a modi- 

 fication of the Insectivora for pursuing their prey in the air. Verte- 

 brte of the trunk. Skull : smooth thin cranium ; moveable and incon- 

 stant premaxillaries ; slender zygomata. Carinated sternum : scapula 

 and large coracoid : powerful clavicles : ulnar patella : elongated 

 fingers. Open pelvis. Bones of tlie hind-Hmbs. Peculiarities of 

 the skeleton of Bats compared with that of other Mammals, of Birds 

 and of Pterodactyles. 



LiiCTUREs XX. and xxr. — Camivora. — The families of this order 



