REVISION OF CARCHARHINID SHARK GENERA — SPRINGER 563 



preservation procedures. The snout tip is one of the most important 

 reference points on a shark, yet in numerous preserved specimens 

 the tip has been pushed in, mashed, or crushed beyond reconstruction 

 because the specimen has been forced into too small a bottle. 



During the course of this study it became apparent that any given 

 character — counts, fin shapes, fin positions, etc. — could vary widely 

 within a species. Usually there would be at least one character in 

 which each specimen of a particular species differed widely from all the 

 remaining. The natm^e and extent of this variation was greater than 

 I expected from my experience with teleostean fishes. For this reason, 

 the reader should make allowances for variability when trying to fit his 

 own specimens to my descriptions. 



Total length (t.l.) : Each specimen was laid on its side in a normal 

 position on a standard fish measuring board (i.e., the caudal fin was 

 not stretched to its fullest extent toward the midline of the body axis 

 but was placed at what appeared to be its normal angle to the body) . 

 The total length is the distance from the tip of the snout (along the 

 projected midline of the body axis) to a point on a vertical line through 

 the tip of the upper lobe of the caudal fin. 



This measurement contains two errors: (1) Because a shark in 

 contour has a broad head and a narrow tail, the sagittal plane of its 

 body is not parallel to the measuring board when the side of the shark 

 is laid flat on the board. The total length measm'ed along this in- 

 clined plane is shorter than the total length measured when the tail of 

 the specimen is raised to make the sagittal plane parallel to the meas- 

 uring board. The amount of error depends on the relative thicknesses 

 of the head and tail. 



(2) Total lengths of various sized specimens cannot be measured 

 comparably because in many of the larger specimens there is a tend- 

 ency for the axis of the upper caudal lobe to become raised in relation 

 to the horizontal axis of the body. Thus, proportional measurements 

 based on total lengths of large specimens appear greater than those 

 based on the total lengths of smaller specimens, which may not actu- 

 ally be the case. (The angle also varies somewhat in sharks of the 

 same size.) 



Snout tip to — 



outer nostrils: A straight pencil line was drawn between the 

 anterior margins of each nostril. One point of a pair of dividers was 

 placed on the tip of the snout and the other on the center of the line. 

 The distance between the two points of the dividers was measured. 



eye: Pencil lines were extended ventrally from the anterior rim 

 of each orbit and joined on the underside of the head. One point of 

 the dividers was placed on the tip of the snout and the other on the 

 center of the line. The distance between the two points of the dividers 

 was measured. 



