GLOSSARY OF TECHNICAL TERMS. 375 



tlieir separation. Thus, " D. X, 12," describes a single dorsal fin with 

 10 spines and 12 soft rays ; " D. X — 12," indicates two dorsal fins — 

 the first of 10 spines, the second of 12 soft rays ; " D. X — I, 12," 

 would indicate the presence of a single spine in the second dorsal. 



The posterior soft ray of the dorsal and anal fins is usually split to 

 the base. It should be counted as one ray and not as two. 



" Gill rakers 5+15," indicates 5 above and 15 below angle of gill- 

 arch; rudiments not counted. When the number above the angle is 

 uncertain or non-essential, it is indicated as " x." 



Lat. /. = Lateral line, i. e., the number of scales contained in its course. 

 When the lateral line is obsolete, " lat. 1." signifies the number 

 of scales in a row from the head to the base of the caudal fin. 

 Thus, " lat. 1. 36 " means that there are 36 scales in a row along 

 the sides from the head to the caudal. 



" Scales 5-36-10 " indicates the presence of 36 scales in the lateral 

 line itself ; 5 scales in a vertical series between front of dorsal and 

 lateral line, and 10 scales between lateral line and vent. 



In all cases the number of rays or scales, as given in the descrip- 

 tions, is intended to represent a fair average, and a variation of one- 

 sixth, or even more, in either direction need not surprise the student. 

 Generally the spines and scales are more constant in their numbers 

 than the soft rays, and the fewer of either, the less variable. 



Length, as used in proportionate measurements, is distance along the 

 side from tip of snout to end of last vertebra. It does not include the 

 caudal fin. 



Depth in length. = The greatest depth of the body as contained in the 

 distance along the side from the snout to the base of the caudal. 



Head in length. = The distance from the snout along the cheeks to the 

 extremity of tlie opercle, as contained in the distance from the 

 snout to the base of the caudal. 



Eye in hend,^= Its longitudinal diameter as contained in the length of 

 the side of the head. 

 As above stated, these measurements, as given in the descriptions, 



are intended to be the average of living adults, and must be applied to 



young specimens or preserved ones with caution. 



Young fishes are usually but not always more elongate than adults, 



and the eye is proportionally much larger. 



A fin is said to be " long " when it has a long base, or is many-rayed. 

 A " high " fin is one in which the individual rays are elongated. 



II. TJeptiles. 



Z. = Length in inches of an adult example, from tip of snout to tip of 



tail. 

 Sc. or iSra/rs. = Number of longitudinal rows of scales exclusive of the 



ventral series. 



