MAfRAUCHKXIA. 



MACIIAIVIIK.NIA. 



672 



vertebral artery in a section exposing the spinal canal Professor 

 Owen then goei on to show that the vertebra of the Macrauckcnia 

 alo closely resemble the middle cerrical vertebra of the Vicuna and 

 Llama in their elongated form; approaching the Auchenial division of 

 the CameUdrr, and deviating from the True Camels in the relation! of 

 the length of the body of the vertebra to its breadth and depth, and 

 in the much smaller size of the inferior processes. The author 

 observes that, excepting the Giraffe, there is no existing Mammal 

 which possesses cervical vertebra so long as the Macrauchene ; but 

 that the cervical vertebra of the Giraffe differ in the situation of the 

 perforations for the vertebral arteries, and in the form of the terminal 

 articular surfaces. Both the cervical vertebnc described by Professor 

 Owen are of the same size, and each measures 64 inches in extreme 

 length, 2 inches 10 lines in breadth, and 2 inches 4 lines in depth. 

 Among the peculiarities of structure, a small longitudinal process 

 (Jig. 2, e) is given off immediately below the base of the anterior 

 process, and this is not observable in any of the cervical vertebra of 

 the Giraffe or Camettdte. In the form of the articulating surfaces of 

 the bodies of the vertebra, the Macraucheue deviates from the Giraffe 

 and Camel, but resembles the Auclttnice. The anterior articulating 

 surface is convex and almost hemispheric in the Giraffe and Cume), 

 whilst the posterior surface is proportionally concave, so thnt the 

 vertebra) of the neck are articulated by ball-and-socket joints, yet nut, 

 as in most reptiles, with intervening synovia! cavities, but by means 

 of the concentric ligamentous invertebral substance characteristic of 

 the Mammals. The degree of convexity and concavity in the articular 

 surface of the bodies of these vertebra! in the Llama and Vicuna is 

 much less than in the Camels, and the former consequently carry their 

 necks more stiffly and in a straight line. The anterior articulating 

 surface in Macrauclienia is less convex than it is in the Llama, ana 

 the posterior surface is less concave. From an analysis of the com- 

 parative structure of these vertebnc in the Camels, the Llamas, and 

 the Macrauchene, Professor Owen infers that the latter carried its 

 neck in the same stiff and upright position as is manifested in the 



There is not in the collection a fragment of dorsal vertebnc, ribs, 

 or sternum ; but the seven lumbar vertebra) form a consecutive series 

 from the same individual as that to which the cervical vertebnc 

 belonged; and though these lumbar vertebra do not possess such 

 distinctive characters as those of the neck, they contribute not unim- 

 portantly to the illustration of the osteology of the animal and its 

 affinities. No existing Pachyderm has more than six lumbar vertebra ; 

 the Camels and Llamas only, among the Ruminants, possess seven ; and 

 here Professor Owen discovered modifications of form in which the 

 Macraucbene deviates from the Vamrlida; and approaches the Horse and 

 Hippopotamus. In the Maerauchenia, as in the Rhinoceros, Tapir, 

 Hippopotamus, and Horse, the transverse processes of the hist lumbar 

 vertebra are of considerable thickness and extent^ and are joined by 

 eoarthrosis to the transverse processes of the sacrum ; but the bony 

 structure of these joints would indicate that they were not subject to 

 be obliterated by anchylosis. 



Sufficient of the sacrum and ossa innominata remain to enable Pro- 

 fessor Owen to state that the sacrum was anchyloscd to the ilia : the 

 lower boundary of this anchylosis is marked below by an external 



: '.' .-.. I !-y x I* '.1 .1- 0*ad|SJsd POOD - ill tin- .MI) -t'.IK ..ftli.- I...,,,.. 



as in the Hippopotamus. 



Lut lumbar vertebra of Jfarrauclirnia, one-third natural ilxc. 



Of the remaining portions, the anrhy loncd fore arm and leg, ami the 

 fora foot are the most characteristic. The portion of the antebrachium 

 which is preserved presents a condition of the radius and ulna inter- 

 mediate to those which respectively characterise the same bones in 

 the Pachyderms and Camels. In the former the radius and ulna are 

 separate bones, united in the same position by a ligament, but so 

 organised that the movement of supmation cannot be effected. A 

 bony confluence joins these bones partially in the ordinary Ruminants, 

 but this rarely extends to the proximal extremities. In the Camel 

 and the Llama the anchylosis is complete, so that no trace of the 

 original separation of the radius and ulna is perceptible; and the 

 olecranon, or elbow, appears as a mere process of the radius. The 

 anchylosis in Macrauclienia is also complete, but the boundary-line is 

 clearly denned, and the proportion which each of the bones contributes 

 to the great articulating surface for the distal end of the bumerus is 

 easily distinguUhable. 



Professor Owen goes on to remark that the confirmation of the close 

 affinity of the Macrauckenia to the Pachydermatous order, which the 

 iitructure of the cervical vertebra above might have rendered very 

 doubtful, is afforded by the bones of the right fore foot. 



Proximal extremity of anchyluicd ulna and radius of the Mocrauchenf, one. 

 fourth natural sine. 



These are in so perfect a condition as to make it certain that the 

 Macrauchene had three toes on the fore feet, and not more ; and that 

 the fully-developed matacarpol bones are distinct, and correspond in 

 number with the toes, not being anchylosed into a single cannon-bone 

 as in the Ruminants. The bones preserved are the rnat.tcarp.iU, 

 proximal phalanges, and middle phalanges of each of the three toes, 

 and the distil or ungue.il phalanx of the innermost toe. 



a, bonci of the light fore foot of the Macrauchcnt, one-fourth natural t'm ; 

 li, necond snd but, or ungueal phalanx, one-half natural *ir.r. 



The author observes in continuation that the bones of tlie leg of the 

 Macrauchene exhibit the same transitional structure as is afforded l.y 

 the definable limits of the nnchylonod bones of the fore arm. In the 

 Pachyderms the fibula is entire and distinct. In the Ruminants (the 

 small musk-deer excepted, and, in an inferior degree, the elk) the 

 fibula appears only as a short continuous process sent down from the 

 under part of the external condyle of the tibia. In the CanuKdai the 

 only trace of the fibula is a still more rudimentnl state of this process, 

 whilst in the Macrauchene the fibula is indeed entire, but it is con- 

 fluent with the tibia through nearly its whole extent The fibula and 

 tibia are distinct bones in both the Palceothcre and Anoplothcrr. 

 It is to the former genus, and especially to Pala-olherinm magnum, 

 that the Macrauchene presents the nearest approach in the general 

 form of the tibia, the principal leg-bone ; but in the Macrauchene the 

 tibia is relatively shorter and thicker and etruighter, and less expanded 



