226 REPORT— 1873. 



The following bones have been identified in the sknlls of Labyrin- 

 thodonts : — 



Premaxillaries (one or two). Supratemporals (two). 



MaxiUaries (two). Quadrato-jugals (two). 



Nasals (two). Snpraoccipitals (one or two). 



Lachrymals (two). Exoccipitals (two). 



Frontals (two). Parasphenoid. 



Prefrontals (two). Pterygoids (two). 



Postfrontals (two). Palatals (two). 



Postorbitals (two). Vomers (two). 



Jugals (two). Quadrates (two). 



Parietals (two). Mandible (each ramus consisting 



Squamosals (two). normally of three pieces, viz. 



Epiotics (two). articular, angular, and dentary). 



There may thus be forty-seven distinct elements i)resent ; and this is appa- 

 rently the number in Lo.vomma (PL I.). 



In Trematosaurus the premaxillaries are nnited. According to Cope * 

 there is no quadrato-jugal in Pariostegm, but the maxillaries have a free 

 termination behind. Pteroplax appears, from at least three well-preserved 

 specimens, to have no maxillaries, resembling in this respect the recent 

 Siren ; it wants also the postero-lateral ossifications external to the level of 

 the orbits f. In Batracliiderpeton the maxiUaries are undoubtedly absent, 

 and the premaxillaries have a free posterior termination %. AH the well- 

 presei-ved mandibles hitherto examined have consisted of three pieces only 

 in each ramus. Burmeister has described six elements as present in a 

 shattered mandible of Trematosaurus § ; and Mr. Hancock records a splenial 

 piece in the mandible of Anthracosaurus ||. The jaw upon which this latter 

 determination is founded is fragmentary, and the internal plate in question 

 may prove to be part of the articular bone. At the time of the publication of 

 the ' Palaontologie Wiirtembergs,' Von Meyer seems to have attributed six man- 

 dibular elements to Mastodonsaurus (pp. 18, 25) ; but this is certainly erroneous. 

 Prof. Huxley spealcs of a splenial in Pachijgonia and Gonioghjptus. 



The general disposition of these bones is similar to that of the Crocodilian 

 skull. The resemblance is closer as regards the bones of the upper surface 

 than with respect to those which compose the palate, and it does not hold 

 good at all of the axial elements of the skull. The occipital and s])henoidal 

 ossifications diff'er essentially from those of the Crocodile or any other reptile. 



The superior surface of the skull is interrupted by five openings, viz. two 

 nasal apertures or external nares, two orbits, and a parietal foramen. The 

 apertures of the ears are situate at the junction of the superior and posterior 

 surfaces, adjacent to the epiotics. There are no lateral-temporal If or supra- 

 temporal fossse, as in CrocodiUa, nor any of the spaces unoccupied by bone 

 which, in addition to the nasal apertures and orbits, break up the roof of the 

 cranium in most existing Amphibia. {Dasyceps has a " facial fontanelle "«*.) 



* Trans. American Philosophical Society, vol. siv. N.S. pt. 1, p. 10 (1870). 

 t Nat. Hist. Trans. Northumberland and Durliam, vol. iv. pt. 1, p. 216 (1871'). 

 % Ibid. p. 216. 1 i ^ ; 



§ Die Labyrinthodonten aus dem bunten Sandstein, pt. 1, pp. 38-41 (1849). 

 II Nat. Hist. Trans. Northumberland and Durliam, vol. iv. pt. 2, p. 388 (1872). 

 ^ Lateral-temporal fossre have been supposed to occur in Zygosaiiriis. See p. 235 

 (footnote). 



*» See appendix by Prof. Huxley to Howell's " Memoir on the Geology of the Warwick 

 Coal-field," Mem. Geo]. Survey, p. 54. 



