CONTENTS 



Sub-Grade 1. CHONDRICHTHYES .118 



Placoid scale, 119 ; Dentine, 119; Ceratotriehia, 122 ; Gill slits 

 and rays, 123; Classification, 123. 



DIAGRAM OF PHYLOGENY, 124 

 Sub-Class 1. ELASMOBRANCHII 125 



Nostrils, 125; Lateral line, 125; Brain, 126; Pectoral fin- 

 skeleton and archipterygium, 127 ; Pelvic fin, 128; Claspers, 

 129.; Urinogenitals, 131 ; Viviparity, 134. 



Order 1. SELACHII .... 135 



Centra, 135 ; Skeleton, 137 



Group 1. 



Sub-Order 1. NOTIDANI 139 



Fain. 1. Chlamydoselachidae, 142 ; Fam. 2. Notidanidae, 143. 



Group 2. 



Division A .... 143 



Sub-Order 1. HETERODONTI .... 143 



Fain. 1. Cestraciontidae, 145; Fain. 2. Cochliodontidae, 146 ; 

 Fam. 3. Edestidae, 147. 



Division B .... 148 



Subdivision 1. 



Sub-Order' SCYLLIOIDEI 148 



Fam. 1. Scylliidae, 149 ; Fam. 2. Lamnidae, 149 ; 

 Fam. 3. Carchariidae, 150. 



Subdivision 2. 



Sub-Order L'SQUALIFORMES . ■ .151 



Fain. 1. Spinacidae, 151; Fam. 2. Pristiophoridae, 152. 



Sub-Order 2/ RAJIFORMES .... 153 



Tribe 1, 155. 



Fam. Squatinidae, 156. 



Tribe 2, 158. 



Group A. Rhinoraji, 159. 



Fam. 1. Rhinobatidae, 159 ; Fain. 2. Pristidae, 

 160 ; Fam. 3. Rajidae, 160. 



Group B, Torpedinoidei, 161. 

 Fam. Torjiedinidae, 161. 



Group C. Centrohatoidei, 163. 



Fam. 1. Trygonidae, 164 ; Fam. 2. Ptychodontidae, 

 165; Fam. 3. Myliobatidae, 165 ; Fam. 4. Psamino- 

 dontidae, 167. 



Incertae sedis. Fam. 5. Petalodontidae, 167. 



