20 PROCEEDINGS OF THE NATIONAL MUSEUM vol. 119 



of either second dorsal or pectoral fins; rostral fenestra present; 

 anterior-median pores on ventral surface of head as in figure 22d.* 

 Sphyrna lewini (Griffith and Smith) 

 Circum tropical in distribution; common in all warm seas. 



*Sphyrna covardi Cadenat keys out to this point, but was not included here since a whole specimen was | 



not examined. It diSers from S. lewini, however, in having a deeper and more robust head (pi. 9) , in minor j 



differences in the chondrocranium (pi. 10), in having the anteriomedian pore patch completely instead of 

 partially divided, and (according to the original description) in having the tips of the pectoral fins white. 



Dignaosis of Family and Genus 



Distinguished primarily by the shape of the head, which is expanded 

 laterally, and which is accompanied by a corresponding modification 

 of the chondrocranium. Eyes situated at tips of lateral expansions, 

 and nares situated at varying distances along anterior margin of head. 

 Olfactory capsules and orbital region widely expanded, and the three 

 rostal cartilages broadly expanded where joined anteriorly. Midline 

 of back posterior to first dorsal fin without a middorsal ridge. Second 

 dorsal fin always much smaller than first dorsal. Body compressed, 

 the depth of the trunk (measured at origin of first dorsal) from 4 to 5K 

 times in distance from tip of snout to upper precaudal pit. Caudal 

 peduncle about two-thirds as wide as deep. Upper precaudal pit 

 strongly developed. Lower precaudal pit present in some species, 

 absent in others; when present, not as prominent as upper pit and only 

 about half as wide. 



Subgenus Eusphyra Gill 



The subgenus Eusphyra, which includes only Sphyrna blochii, is 

 distinguished by the following unique characters: Head extremely ex- 

 panded, the greatest width from 42.0 to 49.2 percent of total body 

 length; outer narial groove present; total number of vertebrae few (117 

 and 124 in two specimens examined); body vertebrae 51 to 54, there 

 being from 15 to 16 fewer body than caudal vertebrae; vertebrae over 

 posterior part of coelomic cavity expanded in size; upper precaudal pit 

 merely a narrow longitudinal groove (fig. 21a); orbit separated from 

 nares by a distance many times diameter of orbit; a unique anterior- 

 median pore patch on underside of head, the patch characterized by a 

 sharp, pointed angle at outer-posterior corner and a more or less 

 straight posterior edge (fig. 22a); and various chondrocranial charac- 

 ters (pi. 5). 



Sphyrna (Eusphyra) blochii (Cuvier) 



Figures 5, 21a, 22a; Plates 1, 5 



Squalus zygaena (misidentification) Bloch, 1785, vol. 1, pi. 117. (Figure.) 

 Zygaena blochii Cuvier, 1817, p. 127. (Original description [in footnote]: 

 "Ajoutez I'espfece representee par Bl. 117, reconnaissable k ses narines 

 placees bien plus prfes du milieu [Z. Nob. Blochii]. Sa deuxifeme dorsale est 



