224 W. BALDWIN SPENCER. 



the extensive group of extinct forms classed together as 

 Labyrinthodonta, and usually regarded as the extinct repre- 

 sentatives of the class Amphibia. On the contraryj one of 

 the most interesting features in the cranial skeleton of these 

 is the possession of an extremely well-marked and prominent 

 parietal foramen,^ which is proportionately quite as large, and 

 in many cases larger, in comparison to the size of the skull 

 than in living Lacertilia. 



There is no doubt that the presence of a parietal 

 foramen is intimately associated with a high state of 

 development of the epiphysis, and we are thus brought 

 without hesitation to the conclusion that, whilst amongst living 

 Amphibians the epiphysis is present only in a rudimentary and 

 degenerate condition, in extinct Amphibia (Labyrintho- 

 donta) the epiphysis was in a high state of spe- 

 cialisation. Further, the only group of living animals in 

 which, as before said, a parietal foramen is present, is Lacer- 

 tilia. Within this group, though various degenerate forms 

 are seen, yet, inasmuch as 



The organ is found in genera of every family, ancient and recent alike (in 

 Hatteria, in Calotes, in Agama, in Moloch, in Anolis, in Iguana, in Anguis, 

 in Varanus, in Seps, in Lacerta), in which a foramen is developed ; whilst 

 again, in such as Gecko, Ameiva, and Ceratophora, where no foramen persists, 

 the organ is absent. 



It may be further said that the presence of a parietal 

 foramen, as a structure typical of the skulls of a 

 group of animals indicates the presence of a pineal 

 eye within that group. 



It is quite true that in three forms described — Cy clod us, 

 Chameleo, and Lyriocephalus — the foramen is present, 

 and though the epiphysis is, in certain respects, highly deve- 

 loped in each case, the distal portion retaining its connection 

 with the brain roof, yet no true eye is formed. This, however, 

 need present no difficulty in the way of acceptance of the 

 above statement. Regarding the present families of Lacer- 



* See especially the drawings of Fritsch in ' Fauna der Gaskohle und der 

 Kalkslein,' Prag., 1885. 



