432 ZOOLOG ¥. 
available for western students who have not access to speci- 
mens of the cunner. 
The perch has the general form of a flattened spindle, for. 
it tapers down at either end and is compressed laterally. 
There is no neck marked off externally, and the head ap- 
pears as the direct continuation of the body, but separated 
from it by a fissure on either side; this is the opening of 
the gills, which extends from above downwards and curves 
forward, nearly meeting its fellow on the median line of the 
under jaw ; upon opening the gill-slit the pectinate or comb- 
like gills or branchiz are seen within. There are four sets 
of branchial filaments, each set attached to a separate de- 
scending arch, in front of each of which isa slit leading into 
the cavity of the mouth ; but there is no slit behind the 
last gill. The branchie are protected externally by the gill- 
cover or operculum, which is attached in front, but is free 
behind, where it forms the front edge of the gill-slit ; it is 
composed of four distinct parts: 1. The preoperculum 
nearest the eye, and with its lowest corner almost a right 
angle ; its posterior and vertical edge is furnished with 
numerous minute projecting spines. 2. Appended to the 
underside of the margin thus armed is the operculum. 3. 
Below the preoperculum is the interoperculum, which par- 
tially covers up 4, the suboperculum. ach of these parts 
has a separate bony support ; all four bones are developed 
only in the Teleosts; in sturgeons, for example, there is 
only an operculum, to which in other Ganoids other parts 
are added; in Selachians the whole apparatus remains 
undeveloped. 
The mouth is placed in front ; the upper lip is capable of 
independent motion, being supported by the premaxillary 
bones, which are but loosely attached to the cranium, though 
in many other fishes the union is closer. The eyes are large 
and lidless ; just in front of each eye is an opening of the 
size of a pin’s head ; these openings lead into the nasal sacs, 
of which there are two, but both are without communica- 
tion with the mouth; in higher vertebrates, from the Dip- 
not upwards and in Myzine, there is such a communication. 
In the Marsipobranchii there is but a single median nasal sac. 
