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. 



Chiniaera 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. tnonstrosa L., King of the Herrings ;• 

 attains 3 or 4 ft. 



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

 without filament ; svu'face waters, N. Pacific. 



Callorhynchus Gronov. Snout with a cartilaginous prominence ending: 

 in a cvitaneous 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 p 

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

 mylus Smith, Upper Jurassic, etc. 



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

 vonian ; Squalorajidae, known by its skeleton, from the Lias ; Mybia- 

 CAi^^THiDAE, also known by skeletons from the Lias and Upper Jurassic, 

 are placed here. 



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

 Mem. Geol. Soc. U. Kingdom, 1878. 



