GREAT LAKES COREGONIDS 



307 



Occiput (O). — Measured from the junction of the premaxillaries to the end of the 

 supraoccipital bone, not to the beginning of the scales. The exact point was deter- 

 mined by feeling with a sharp instrument. 



Snout (S). — Measured from the junction of the premaxillaries^to the anterior 

 bony margin of the orbit. The dividers were inserted into the eye socket. 



Maxillary (M). — This is in reality a measurement of the upper jaw and is taken 

 from the symphysis of the premaxillaries to the caudal end of the maxillary bone. 



Mandible (J).— Measured from the articulation of the articular with the cranium 

 to the symphysis of the dentaries. 



Eye (E). — The measurement given is the horizontal diameter of the eyeball, 

 not the distance across the cornea. Dividers were inserted into the eye sockets and 

 their points brought against the eyeball at the ends of its longitudinal axis. Care 

 must be taken not to compress the ball in fitting the divider points. 



Fin length (P, V, Ad). — Measured from the origin of the fin to the tip of its 

 longest ray, or, in the case of the adipose, to its distal end. 



Fin bases (DB, AB). — The length of the base of the dorsal and anal fins. 



Dorsal coefficient (DC). — The height of the dorsal divided by its base. 



Anal coefficient (AC). — The height of the anal divided by its base. 



Pectoral-ventral distance (PV). — The distance between the anterior ends of the 

 insertions of the pectoral and ventral fins. 



Ventral-anal distance (AY). — Measured from the anterior end of the insertion of 

 the ventral fin to the corresponding point of the anal. 



Depth (D). — -The greatest vertical depth of the body measured with calipers. 



Width (W). — The greatest width of the body measured with calipers. 1 1n 

 bloated specimens the width was taken in the region of the lateral line. This char- 

 acter is very unsatisfactory, inasmuch as the width of the body very frequently has 

 been reduced by artificial compression in the preserved material. 



Counts 



Gill rakers (R). — The left arch, after being carefully removed with a sharp 

 scalpel, was held completely spread out, and the counts were then made. (Care 

 must be taken, in removing the arch, that no rakers are lost at the ends.) By this 

 method the number of gill rakers on each part of the arch can be determined readily. 

 Every visible raker has been included in the counts. 



Scales in lateral line (SC). — In specimens with all their scales only those scales 

 with pores were counted. In some specimens a few scales at the caudal end of the 

 line lack pores. These have not been included in the counts. When scales had 

 been lost accidentally from the lateral line, however, the scale pockets were counted 

 throughout the entire length of the lateral line. 



Longitudinal scale rows. — These were counted around the body at three loca- 

 tions — (1) just in front of the dorsal and ventral, (2) just in front of the adipose and 

 the anus, and (3) around the caudal peduncle just behind the adipose and anal. 

 The rows run lengthwise of the fish and can be counted easily except in the proximity 

 of the fins. In front of the dorsal and adipose fins and behind the adipose and anal 

 fins there frequently are developed very short rows, comprising sometimes only one 

 or two scales All these were considered rows and were included in the counts. 



