TYLOTOTEITON. 859 



and both tlie ceratohyal and thyrohyal are free and covered by the forepart of the 

 paratoids. They are invested in a sheath of fascia and attached to the back of the 

 skull by a fine ligament, bnt they are not in contact with any of the bones of the 

 skuU. 



Dr. Strauch, the most recent writer on the value to be attached to the structural 

 differences manifested by the TJrodela, has sub-divided them into two great sections, 

 depending on the distribution of the palato-vomerine teeth, whether they are in the 

 longitudinal series Mecodonta,OY in transverse more or less oblique series Zechriodonta. 

 This genus falls, therefore, under the Mecodont division, which includes, according to 

 Dr. Strauch, only Triton and five other genera, viz., Salamandra, Fleurodeles, 

 Bradyhates, Chioglossa, and Salamandrina. To the first-mentioned genus, Strauch 

 refers a number of Amphibians, which have hitherto been considered by many 

 naturalists to represent generic types, e. g., Triton, NotopMJialmus, JEuproctus, Cynops, 

 Tariclia, Lopliinus, and Ommatotriton; but if his view were accepted, Tylototriton, if 

 judged by its skull alone, would perhaps be regarded as only a form of Triton, 

 Strauch sub-divides the genus Triton into two sections, characterized by the absence 

 or presence of a fronto-temporal arch, as he does not consider the osseous bridge 

 formed by the frontal and temporal so important a structure as to let its presence 

 or absence determine a genus, and moreover, he has pointed out that Leydig has 

 shown that the form of the arch goes hand in hand with other organic similarities 

 of structure, with the exception perhaps of those which are sexual. The males, 

 however, of some species, for example, in which the fronto-temporal arch is wanting, 

 or merely indicated by a ligament, have at the breeding season a high crest, whilst 

 males possessing a well- developed arch may not have a crest, while others, such as 

 Ommatotriton vittatus, which Gray considered a very distinct genus, may have 

 a crest. 



The differences existing between the skulls of the various forms of Amphibians 

 referred by Strauch to the genus Triton would probably be considered of generic 

 importance if they occurred in higher groups of vertebrates. In estimating the 

 value of skull characters in this group however, the consideration of the remarkable 

 changes which the cranium undergoes after the animal has left the e^^ has to be 

 borne in mind, as these changes would seem to indicate a greater capacity in the 

 skull of these Amphibians to variation than occurs in the skulls of other and higher 

 animals, which are not the subject of any remarkable modifications after birth. 



Tylototriton, however, presents certain characters which seem to separate it gen- 

 erically from all other Mecodont Urodela, more especially as they are associated with 

 other features which are not common to any other Amphibians. The skull characters 

 are the remarkable osseous crest which runs round the margins of the upper surface 

 of the skull and the shorter crest along the parietals, each of these structures being 

 deeply fitted for the reception of the remarkably large cuticular glandular pits 

 which densely stud the skin, and are always packed full of secretion, and a perfect 

 ptyergoid arch reaching the maxilla, the latter bone prolonged right up to the 

 quadrate, to which it is attached by a ligament. Associated with these characters 



