210 PROCEEDINGS OF THE ACADEMY OF 



MiCROSAURIA. 



Vertebral centra ossified ; no branchial hyoids ; teeth simple or with slightly 

 inflected enamel, jileurodont. Occipital condyles. 



Ganooephala. 



Vertebral centra cartilaginous ; branchial hyoids present ; teeth with slightly 

 inflected enamel, anchylosed by their bases. No ossified occipital condyles. 



Labyrinthodontia vera. 



Vertebral centra osseous ; no branchial hyoids ; teeth with much inflected 

 enamel, anchylosed by their bases. Occipital condyles. 



Xenorhachia. 



This order I proposed for the reception of the genus Amphibamus Cope, in 

 1865. I proposed to regard, as one of its characters, the existence of opistho- 

 coelian vertebris. Such impressions were observed in the matrix in which the 

 fossil was preserved, as to induce a belief in the existence of such vertebra?, 

 and the existence of these in a well ossified condition, in the apparently nearly 

 allied genus Pelion Wyman, strengthened such belief. There were actually, 

 however, only osseous neural arches present, and I am now decidedly of the 

 opinion that the vertebral centra were either cartilaginous or annuliform, as in 

 Archegosaurus, 



. AMPHIBAMUS Cope. 



Proc. Acad. Nat. Sci. Phila. 1865, 134. 



Amphibamus grandiceps Cope, Proc. Ac. N. Sci. Phila. 1865, p. 134. Palaeon- 

 tology 111. State Survey. Tab. 

 Carboniferous ; Lower Coal Measures, Morris Co., Illinois. 



MiCROSAURIA. 



This sub-order was established by Prof. Dawson, for small lizard-like verte- 

 brates from the Coal Measures, which he thought presented points of affinity 

 to, or should be under the Saurian reptiles, at the same time recognizing Ba- 

 trachian characteristics. 



After examining the evidence brought forward by Prof. Dawson, it appears 

 to the writer that the Saurian characteristics are analogical only, and not in- 

 dicative of true affinity, and that these creatures form, in fact, a series closely 

 resembling or parallel with what was probably an immature stage of the 

 Labyrinthodontia. They are in fact Labyrinthodonts, with simple or very 

 slightly inflected enamel of the teeth, and with tlie extent of the exostosis of 

 the cranial bones much reduced. This character has been much overrated by 

 some authors. In the Dendrerpeton obtusum Cope the grooving and pit- 

 ting exists only on the posterior parts of the cranium, and gradually disappears 

 anteriorly. In the Alligator mississippiensis the same is the case. 



The points in which they have been said to resemble the Lacertilia, are, 1st, 

 the dermal scales ; 2d, the parietal fontanelle; 3d, possession of ribs. All of 

 these features belong to the Labyrinthodontia ; the Xenorhachia also had 

 scales. On the other hand, the two occipital condyles, indicating the existence 

 of a parasphenoid bone, distinguishes it at once from all the Allantoid verte- 

 brata, and the form of the vertebras is very Batrachian. In the Lacertilian 

 families of Gecconidae and Hatteriidae only we have biconcave vertebra, but 

 the concavities are comparatively shallow, and the vertebrae less constricted 

 medially than in the Microsauria. Those of the latter are much like those of 

 Salamanders, according to Prof. Dawson's figures. 



The bones figured as pelvic ai'e unlike those of any Batrachia or Lacertilia 

 known to the writer. But until those of the Labyrinthodontia are discovered, 



[Sept. 



