DESCRIPTIVE TERMS. 761 
10. Upper pharyngeals, two sets of bones, usually rounded, placed on the upper side of 
_ the’ceesophegus, behind the gill arches. 
11. Lower pharyngeals, one on each side of the median line, below the esophagus, and 
behind the gill arches. These bones are modified gill arches, and their forms vary much 
with the different suborders of fishes, and their structure is of great importance in the 
system of classification. In the Black Bass they are flattish and somewhat triangular ; 
in the Sucker they are sickle-shaped. | 
The comparative size of the head is described by noticing how many times its length 
(along the side, from the snout to the posterior edge of the opercle), is contained in the 
length of the body (measured along the side from the tip of the snout to the middle of the 
base of the caudal fin), Thus ‘‘ head 44 in length” (asis the case in the Sucker) in- 
indicates that the length of the head is a little less than one-fourth that of the head 
and the bedy. ‘The length of the head is proportionately rather greater in young fishes 
than in adults. | 
_ Below the subopercle and interopercle, and nearly parallel with them are the bony 
branchiostegal rays enveloped in the gill membranes. ‘These are three in number on each 
side in the Sacker, six in number in the Black Bass, and their number often furnishes 
important characters. : | 
The scales when normally developed, are either Ctenoid (with the exposed or posterior 
edge rough or ciliated as in the Perch or Black Bass), or Cycloid (smooth asin the Sucker). 
In most cases, there is a series of scales along each side, each of which is provided with 
a Mucous iube, these forming a conspicuous raised line known as the lateral line. In | 
many scaleless fishes this chain of mucous tubes is developed. 3 
The relative size of the scales is indicated by counting them. Of course, the smaller 
they are proportionately, the more numerous they are. The number forming the lateral line 
48 one of the most valuable and constant of specific characters, being subject to but slight varia- 
tions. ‘‘ Scales 10-65-7,” the formula ef our Sucker, signifies ten series of scales between 
the dorsal fin and the lateral line; 65 scales in the lateral line, and seven series between 
the latera! line and the ventrals. 
The firs are (a) the paired fins, which are the pectorals (corresponding to the anterior 
limbs or arms) situated immediately behind the gill openings, and the. ventrals (corres- 
ponding to tho posterior limbs) placed either behind or below the pectorals; and (6b) 
the vertical fius, or fins on the median line of the body. These are the dorsal (on the 
back), caudal (on the end of the tail), and the anal (on the lower side, behind the vent). 
The dorsal is sometimes divided into two fins, in which case the anterior is called 
jirst dorsal, the posterior, second dorsal. 
The position of the fins is a matter of much importance. The ventrals are said to be 
abdominal when they are inserted on the belly, notably behind the pectorals, asin the 
Sucker, thoracic when inserted wnder the pectorals or closs behind them, as in the Black 
Bass, jugular when in advance of the pectorals, as in the Cod fish. 
The rays of which the fins are composed may be either spines or soft rays. 
The spines are usually. stiff and pointed, and are never jointed or articulated, and are 
never branched. In those fishes which have spines there is commonly one in each ven- 
tral fin, nove in the pectoral or caudal fins, one or more in the front part of the anal fin 
and several in the anterior part of the dorsal fin, constituting the whole first dorsal 
when there are two dorsal fins. : 
The soft rays are always articulated or jointed towards their tips, and most of them 
are also branched. They are therefore usually wider at their tips than at their bases, 
and are seldom rigid, unless rendered so by drying. In all cases where the dorsal and 
