AND ON THE CLASSIFICATION OF FISH. 539 
. Nyctitantes. 
. Lamnoidei. 
. Alopecia. 
. Cestraciones. 
. Rhinodontes. 
. Notidani. 
. Spinaces. 
. Scymnoidei. 
. Squatine. 
COM Mn H TP OO 
— 
Subordo 2. Raiidz. 
Familie : 11. Squatinoraiz. 
12. Torpedines. 
13. Raiz. 
14. Trygones. 
15. Myliobatides. 
16. Cephalopterz. 
Ordo II. Holocephaili. 
Familia 1. Chimere. 
Subclassis 5. MARSIPOBRANCHII s. CyCLOSTOMI. 
Ordo I. Hyperoartii. 
Familia 1. Petromyzonini. 
Ordo II. Hyperotreti. 
Familia 1. Myxinoidei. 
Subclassis 6. LEpTrocarpIil. 
Ordo I. Amphiozxini. 
Familia 1. Amphioxini. 
APPENDIX. 
I shall add to this treatise some recent physiological observa- 
tions on the true difference between the bulb of the truncus arte- 
riosus in the Plagiostomi and Ganoids on the one hand, and the 
osseous fishes on the other. This point is still susceptible of an 
advantageous physiological development. 
