954 



CLASS PISCES. 



respects, and more especially as regards the dentition, Ceratodus, as 

 pointed out by Dr Fritsch, is, however, much more nearly allied to the 

 under-mentioned family Dipteridce, and it seems advisable to regard 

 it as representing, at least provisionally, the type of a distinct family. 

 Ceratodus is one of the very few instances where a genus, founded 

 upon the evidence of fossil specimens, has subsequently been discov- 

 ered in a living condition. Fossil teeth of this genus were long known, 

 but it was not until the year 1870 that the existence of a living rep- 

 resentative was brought to the notice of science. The body of the 

 Barramundas, as these fishes are termed, is laterally compressed, 

 with one continuous vertical fin ; while the 

 paired fins are paddle-shaped, with a broad 

 fringe. The vomerine teeth (fig. 881, x) 

 are shaped like the incisors of many mam- 

 mals, while those on the palate (ibid., xx) 

 and mandible have an inner smooth con- 

 vex border, and externally bear a num- 

 ber of strongly-marked ridges or horns. 

 In the existing species the teeth of oppo- 

 site sides are separated by a distinct in- 

 terval (fig. 881), but in some fossil forms 

 they were in contact. Again, in the living 

 species, the palatal teeth bear six distinct 

 horns, while the backward production of 

 the inner margin forms an incomplete 

 seventh horn (fig. 881); but in the man- 

 dibular teeth there are not more than the 

 typical six horns. In fossil forms, accord- 

 ing to Professor Miall, the mandibular teeth are slightly smaller and 

 narrower than the palatal ones, and have not more than four horns ; 

 while the palatal teeth have either five horns, or four and a rudi- 

 ment of a fifth (fig. 882); 

 this simpler structure of 

 the teeth in the earlier 

 forms being analogous to 

 that which we have already 

 mentioned as obtaining in 

 the Selachian Notidanus. 

 Some of the fossil teeth 

 indicate individuals of two 

 or three times the size of 

 the Barramunda, of which 

 the largest specimens at- 

 tain a length of nearly six feet. The position of these upper teeth 

 on the palatopterygoid bar is well shown in fig. 881, which also ex- 



Fig. 881.— Mouth of Ceratodus 

 Forsteri. Reduced, x, Vome- 

 rine ; xx, Palatal ; xxx, Mandi- 

 bular teeth ; n, anterior ; «', Pos- 

 terior nares. 



Fig. 882.— The right palatal tooth of Ceratodus His 

 lofiiamis, from the Lower Gondwanas of Maleri, India 

 The left side is the anterior border. 



