138 



CHIM.^ROID FISHES AND THEIR DEVELOPMENT. 



evolved a long way in the direction of the Chimseroid. On the other hand, we 

 must leave entirely doubtful whether Janassa was still retaining the features of an 

 ancestor which gave rise to the Chimseroid, or whether it was a form which was 

 becoming still more Chimsera-like than its ancestor — just as Lepidosiren has 

 become more like the amphibian than has the more primitive Ceratodus. 



121 >'3 '^ 



Figs. 121-125. — Association of dental plates of late mesozoic Chimaeroids. Tritors represented by shaded aieas. 



After specimens in British Museum. Partly after Smith Woodward. 

 121, Ganodus rugulosus; 122, Elasmodus hunter! ; 123, Edaphodon bucklandi; 124. Ischyodus egertoni ; 123, Elasmodecles willelli. 



The Permian fossil Menaspis should also be mentioned in this connection. 

 Whether, however, it can be regarded as Chimaeroid has already been considered 

 by the present writer in a recent number of the American Geologist (vol. xxxiv, 

 pp. 49-53). It was there shown that the size of the dental plates of Menaspis 

 (fig. 1 1 5) indicates that the entire region of the fossil inclosed with spines is to be 



