236 VERTEBRATE ANIMALS. 
ad Ro XV. 
ORDERS OF FISHES. 
THE number of different kinds of fishes is so enormous that 
nothing further will be attempted than merely to give an outline 
of the leading peculiarities which distinguish the different orders. 
The classification here adopted is the one proposed by Professor 
Huxley, who divides the class Pzsces into the following six 
orders :— | 
. Pharyngobranchiz. 
. Marsipobranchiz. 
. Leleostet. 
- Ganoidet, 
. Elasmobranchit. 
. Dipnot. 
Au BRwWN 
ORDER I. PHARYNGOBRANCHII (Gr. Dharynx, the upper part 
of the gullet ; and dvagchza, gills).—This order of fishes includes 
only a single animal, the anomalous Amphioxus, or Lancelet, 
the organisation of which differs in almost all its important 
points from that of all the other members of the class. In fact, 
the Lancelet presents us with the lowest type of organisation as 
yet known in the Vertebrata. ‘The Lancelet is an extraordinary 
little fish, from one and a half to two inches long, which bur- 
rows in sand-banks in various seas, but is especially abundant 
in the Mediterranean. The body is lanceolate in shape, and is 
provided with a narrow membranous border, of the nature of a 
median fin, which runs along the whole of the dorsal and a por- 
tion of the ventral surface, and expands at the tail to forma 
lancet-shaped caudal fin. :There are no true “paired” fins, 
representing the fore and hind limbs. The mouth is a longi- 
tudinal fissure, placed at the front of the head, and completely 
destitute of jaws, but surrounded by a number of cartilaginous 
filaments, The throat is provided with several leaf-like fila- 
