204 PALAEONTOLOGY. 



The ilium (62), like the scapula, is expanded at its articular 

 or femoral end. Two shorter bones on each side complete the 

 pelvis below. The broader one is the pubis (64). The femur 

 (65), is slightly expanded, and truncate at both ends ; it is not 

 longer than the ilium. The tibia (66) and fibula are separate 

 bones, rather more than half the length of the femur. The 

 foot-bones are separated by a fibro-cartilaginous tarsal mass (68) 

 from those of the leg. The form of the phalanges, expanded 

 and truncate at both ends, bespeaks their simple ligamentous 

 joints, and that they supported, like the fore-limb, a fin or 

 limb adapted simply for swimming. 



The argument for the saurian affinities of Arcliegosaurus, 

 based by V. Meyer on the short fore-limbs of Mystriosaurus, 

 already invalidated by the difference of structure, is contro- 

 verted by the fact, that the hind limbs of Arcliegosaurus, like 

 those of the Perennibranchs, are not only as simple in struc- 

 ture, but also as short, as the fore limbs. This laborious 

 observer and accomplished artist has most contributed to 

 our knowledge of the fossilizable parts of Arcliegosaurus; 

 but the true nature and deep significance of his subject 

 seem to have escaped him. It is not with any known reptile, 

 least of all with the crocodile, that it shews such conformity 

 of structure as fully elucidates its affinities. More and 

 truer insight is to be gained by comparison of the Arcliego- 

 saurus with the vertebrates of the Devonian and carbonifer- 

 ous periods. The imperfectly ossified or notochordal state of 

 the vertebral column, is that of all the fishes of its own and 

 antecedent times. The state of the exoskeleton, as rhombo- 

 ganoid scales on the trunk, and broad suturally- united, 

 grooved, and polished plates on the head, are characters found 

 in no air-breather of the present day. Associated as they are 

 with labyrinthic teeth, and with limbs, in the embryonally- 

 batrachian condition of those of a proteus, they seem to offer, 

 to one who attends the facts upon which a science of the 



