ON FOSSIL AND RECENT REPTIL1A. 155 



This embryonic or developmental character is unascertainable in the extinct 

 Archegosaurus and Labyrinthodon. The signs of affinity of Labyrinthodon 

 to Ichthyosaurus, and those structures which have led the ablest German 

 palaeontologists to pronounce the Labyrinthodonts to be true Saurians under 

 the names of Mastodonsaurus, Trematosaurus, Capitosaurus, &c, may well 

 support the conjecture that modifications more ' reptilian ' than those in 

 Salamandra did attend the development of the young Labyrinthodont. 



Characters derived from the nature of the cutaneous coverings equally 

 fail to determine the class-characters of Batrachia as contradistinguished 

 from Reptilia. It is true that all existing Batrachia have a scaleless skin, 

 or very minute scales (Cacilia), but not all existing Reptiles have horny 

 scales. The Crocodiles and certain Lizards show a development of dermal 

 bones similar to that in certain placoid and ganoid fishes. This development 

 characterizes the cutaneous system in the Labyrinthodont genus Anisopus ; 

 and in regard to the dermal ossifications of the cranium, the resemblance to 

 the Ganoidei is closer in those ancient forms of Reptilia which exhibit in their 

 endoskeleton unmistakeable signs of their affinity to fishes and batrachians. 



In the survey which, with a view to communicate its results to the pre- 

 sent Meeting of the British Association, I have made of all the known forms 

 of cold-blooded air-breathing Vertebrates, recent and fossil, I have to ac- 

 knowledge myself unable to define any adequate boundary for dividing them 

 into two distinct classes of Batrachians and Reptiles ; and I am as little able 

 to point out a character dividing the air-breathing from the water-breathing 

 Hcematocmja — t\\e Reptiles from the Fishes. 



In the present Report, therefore, an arbitrary line has been drawn, in order 

 to define its subject, between Lepidosiren and Archegosaurus, and the re- 

 view of the ordinal groups of Reptilia, or air-breathing Hcematocrya, will 

 commence with that of which the Archegosaurus is the type. 



Order I. Ganocephala. 



The name of Ganocephala, for this group or order (yai'os, lustre; K€<j>a\i), 

 head), has reference to the sculptured and externally polished organoid bony 

 plates with which the entire head is defended. These plates include the 

 'post-orbital' and 'super-temporal' ones, which roof over the temporal 

 fossae. There are no occipital condyles. The teeth have converging inflected 

 folds of cement at their basal half. The notochord is persistent, the ver- 

 tebral arches and peripheral elements are ossified, the pleurapophyses are 

 short and straight; there are both pectoral and pelvic limbs, which are 

 natatory and very small ; there are large median and lateral 'throat-plates' : 

 the scutes are small, narrow, subganoid. Some of the fossils show traces of 

 branchial arches. The above combination of characters gives the value of 

 an ordinal group in the cold-blooded Vertebrata. 



The extinct animals which manifest it were first indicated by certain 

 fossils discovered in the sphserosideritic clay-slate forming the upper mem- 

 ber of the Bavarian coal-measures, and also in splitting spheroidal concre- 

 tions from the coal-field of Saarsbriick near Treves; these fossils were 

 originally referred to the class of Fishes (Pygopterus Lucius, Agassiz). But 

 a specimen from the ' Brandschiefer' of Miinster-Appel presented characters 

 which were recognized by Dr. Gergens to be those of a Salamandroid 

 Reptile*. 



* Mainz, Oktober 1843.—" In dera Brandschiefer von Miimlerappel in Rhein-Baiem 

 habe ich in vorigen Jahre « cinen Salamander aufgefumlen ":—" Gehovt dieser Schiefer der 

 Kohlen-formation ?— in dcscne falle ware der Fund audi in audcren Hinsicht interessait." 

 Lconhard und Broun, Nuc Jahrbuch fiir Mineralogie, &c, 1814, p. 49. 



