198 PALEONTOLOGY 



together fishes and reptiles within the limits of such group. 

 The salamandroid (or so-called "sauroid") Ganoids — Lcpi- 

 dosteus and Pohjptcrus — are the most ichthyoid, the true 

 Labyrinthodonts are the most sauroid, of the group. The 

 Lepidosircn and Archegosaurus are intermediate gradations, 

 one having more of the piscine, the other more of the reptilian 

 characters. The Archegosaurus conducts the march of develop- 

 ment from the fish proper to the labyrinthodont type ; the 

 Lepidosircn conducts it to the perennibrauchiate batrachian 

 type. Both illustrate the artificiality of the supposed class 

 distinction between fishes and reptiles, and the natural ity of 

 the " Haematocrya," or cold-blooded Vertebrata, as the one 

 unbroken progressive series. There is nothing in the known 

 structure of the so-named Archegosawi us or Mastodonsa a n< s 

 that truly indicates a belonging to the saurian or crocodilian 

 order of reptiles. The exterior ossifications of the skull and 

 the canine-shaped labyrinthic teeth are both examples of the 

 salamandroid modification of the ganoid type of fishes. 



The small proportion of the fore limb of the Mgslriosaurus 

 in nowise illustrates this alleged saurian affinity ; for though 

 it be as short as in Archegosaurus, it is as perfectly constructed 

 as in the crocodile, whereas the short fore limb of Archego- 

 saurus is constructed after the simple type of that of the 

 Proteus and Siren. But the futility of this argument of the 

 sauroid affinities is made manifest by the proportions of the 

 hind limb of Archegosaurus. As in Proteus and Amphiuma, 

 it is as stunted as the fore limb ; whereas in Mysfcriosa/wrua, 

 as in other Teleosaurians, the hind limbs are relatively larger 

 and stronger than in the existing crocodiles. 



Order .'?. — IeiiTiivoi'iiio gia.* 



The bones of the head still include the supplementary "post- 

 orbitals" and " supra-temporals," but there are small 



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