158 SUB-CLASS ELASMOBRANCHII. 



demibranch on the fourth branchial arch. It is clear from this 

 that the Elasmobranch characters strongly predominate, and 

 in our opinion they may fairly be retained as an order of that 

 subclass. 



Chimaera L., snout soft, prominent, without appendage ; tail produced 

 into a fine filament ; deep water (200 to 1,200 fathoms) of coasts of 

 Europe, N. Pacific, Cape ; C. monstrosa L., King of the Herrings ; 

 attains 3 or 4 ft. 



Hydrolagus Gill, like Chimaera, but three dorsals and caudal, and tail 

 without filament ; surface waters, N. Pacific. 



Callorhynchus Gronov. Snout with a cartilaginous prominence ending 

 in a cutaneous flap ; S. Pacific, Cape ; egg-case 9 or 10 in. x 3 in. 



Hariotta Goode and Bean. Snout elongated, no frontal clasper, anal 

 fin as cutaneous fold, deep water 700 to 1,200 fathoms. 



Extinct genera*: Ischyodus Eg., Upper Jurassic and Lower Cretaceous ; 

 Ganodus Ag. ; Edaphodon Buckl., Cretaceous, Eocene, Oligocene ; Pachy- 

 mylus Smith, Upper Jurassic, etc. 



The extinct families PTYCTODONTIDAE, known by teeth from the De- 

 vonian ; SQUALOBAJIDAE, known by its skeleton, from the Lias ; MYRIA- 

 CANTHIDAE, also known by skeletons from the Lias and Upper Jurassic, 

 are placed here. 



* E. T. Newton, Chimaeroid Fishes of the British Cretaceous Rocks, 

 Mem. Geol Soc. U. Kingdom, 1878. 



