112 
ECHENEI8. 
Tins genus is recognised by having a flat oblong disk on the top of 
the head, which is marked with a double row of transverse raised 
lines or ridges, each of which is furnished with spinous teeth, the 
whole enclosed within a raised border. There is in addition a single 
dorsal and anal fin, and the ventral fins are thoracic. 
There are several species of this genus, but there is reason to suppose 
they have been represented as more numerous than they are, for it 
appears from the observations of Dr. Albert Gunther, in the “Annals 
of Natural History,” March I860, that the number of plaits or laminae 
in the disk or sucking apparatus on the head is subject to variation, 
and in consequence that a scpamtion of species built on such variation 
will lead to error. It appears also that the exact form of the tail is 
uncertain as a distinction; for it is found to vary from the forked 
shape to the round in what may be termed the Common Eemora, as 
the laminae vary also in the same fish from sixteen to twenty. 
Eoufhness of the tongue has also been thought a speeific character; 
but ”in the same undoubted species this has been seen to vary from 
a state of smoothness to decidedly rough. 
All the fishes of this genus may be considered as being only furnished 
with a single dorsal fin; but an attempt has been made to represent 
the sucking apparatus as in its nature an anterior dorsal fin, although 
for special purposes it is made to assume a differemt form from ordinary 
fins. It is the opinion of Voigt that this modification is accomplished 
by the bending of the rays downwards on both sides, to_ constitute the 
disk with its lamin®, and that the very small hooks which are on the 
borders of the lamiri® have the same function as similar formations 
have in the several species of the family of Belides. It is beyond 
doubt that there are examples in nature where an organ hy even an 
apparently small change of structure is rendered capable of performing 
functions which appear very different from those for which it seemed 
originally intended; but more extended examination must be instituted 
before tliis can be considered certain in the present instance; and if 
there be at all a resemblance to a fin in this organ, it would rather 
appear to be in the raised border of the disk than in the lamin®, the 
structure of which appears to be of the nature of cartilage, and which 
rest on a series of bones that communicate with the spinous or upright 
processes of the vertebrie, and are themselves moved by independent 
muscular fibres. These laminm are in pairs, proceeding from a middle 
longitudinal ridge, and in this respect differ greatly from the fins of 
any known fishes. When about to bring this sucking organ into 
action, the fish appears to bring the hooks or rough edge of those 
lamime into contact with the surface on which it is its purpose to fix 
itself; and then, chiefly by means of the raised border of the disk, 
