NO. 3539 HAMMERHEAD SHARKS GILBERT 7 



between the points marked by X (rostral cartilage length) and Y 

 (distance between tips of preorbital cartilage) in figure 3. 



In addition, S. corona and S. media may also be distinguished by 

 difference in snout length. The values have been expressed as a 

 ratio by dividing snout length by head width; these are compared in 

 figure 16. 



In general, determination of the patterns of the Ampullae of Loren- 

 zini on the ventral surface of the head becomes progressively easier 

 with an increase in size of the individual. This is subject to variation, 

 however, even within the same series of specimens. 



LATERAL INDENTATION 

 NARIAL OPENING 

 SUBNASAL PORES 

 SUBOCULAR PORES 

 ■ ORBIT 



•MEDIAN INDENTATION 



ANTERIOR-MEDIAN PORES; 



ANTERIOR-LATERAL PORES 

 INNER NARIAL GROOVE 



OUTER NARIAL GROOVE 



Figure 2. — Ventral side of head, showing important morphological features and mucal pore 

 patterns (terminology of mucal pores adapted from Tortonese, 1950a, p. 9; drawing by 

 Paul Laessle). 



Since a whole specimen of Sphyrna couardi was not available and 

 the head examined was seen after most of the figures were prepared, 

 this species has not been included in the species key, in most of the 

 tables, or in figures 4 and 22. Also, no diagnosis or description is 

 given under the account of the species. 



Information regarding life histories, morphometric changes re- 

 sulting from growth, and zoogeography are usually included in sep- 

 arate sections rather than in the individual species accounts. If, in 

 a species account, there is no discussion of morphological variation, it 

 may be assumed that no noteworthy variation was discovered. New 

 names, new combinations of names, and information pertaining to 

 original descriptions and type material have been included in the 

 synonymies; if the nomenclatm'al history of a species is of sufficient 

 complexity, additional discussion is presented elsewhere in the species 

 I account. More complete synonymies, based on references for the 



