CHAPTER IV. 



TABULAR SCHEME, 



Body horizontal 



Both eyes on upper surface ; mouth on under surface ; no 



gill-cover. 

 Gill-openings lateral Rhina, 237. 



Gill-openings inferior 



Tail without longitudinal fold 

 No dorsal Trygon, 252. 



Dorsal on tail 



Dorsal between ventrals Cephaloptera, 251. 

 Dorsal beyond ventrals Myliobatis, 250. 



Tail with longitudinal fold 



Caudal well developed, wings almost semi-circular 



Torpedo, 248, 249. 

 Caudal rudimentary or absent, wings angular 



Raia, 238-247. 



Both eyes on upper side ; month extending to upper and 



under sides ; gill-covers present 

 Eyes to the left 



Two spines behind left ventral Arnoglossus, 156. 

 No spines behind left ventral- 

 Caudal as long as from snout to pectorals 



Lepidorhombus, 155. 

 Caudal short 



Scales ctenoid and rather large Zeugopterus, 



153, 154- 

 Scales cycloid, and small or absent Rhombus, 



151. 152- 



Eyes to the right 

 Jaws alike on both sides 



Lateral line straight Hippoglossoides, 150. 

 Lateral line curved Hippoglossus, 149. 



Jaws not alike on both sides 



Mouth at end of snout Pleuronectes, 157-161. 

 Snout curving beyond mouth Solea, 162-165. 



Body vertical 

 Caudal fin absent 

 Body tapering 

 Tail filamentary Chimara, 221. 

 Dorsal with a low penultimate section Zoarces, 82. 

 45 



