422 Memoir Sears Foundation for Marine Research 



Distance from snout to: 1st dorsal 28.9, 29.1 ; 2nd dorsal 59.4,60.7; upper caudal 



73-3>74-3j pectoral 21.6, 20.7; pelvics 46.7, 42.7; anal 58.1, 59.2. 



Intersface between: ist and 2nd dorsals 21.6, 22.9; 2nd dorsal and caudal 9.2, 



9.O; anal and caudal 6.9, 7.8. 



Distance from origin to origin of: pectoral and pelvics 24.O, 23.7; pelvlcs and anal 



12.2, 16.5. 

 Trunk at origin of ist dorsal between y^ and ^ as high as its length to origin of 

 caudal, moderately compressed. No mid-dorsal ridge. Caudal peduncle about % as wide 

 as deep, the upper precaudal pit strongly developed with its anterior outline oval or sub- 

 angular, the lower pit only about V2 as wide, but of similar form. Dermal denticles 

 relatively somewhat larger than in zygaena, varying from closely overlapping to loosely 

 spaced, the blades mostly rather steeply raised, usually with 5 strong ridges and as many 

 sharp-pointed marginal teeth (longer than in other local species), the axial slightly the 

 largest; short, slender pedicels. 



Head a little less than Vs (average about 28 to 29%) of trunk to origin of caudal, 

 convex dorsally to opposite the angles of mouth but concave thence forward, very thin an- 

 terior to the eyes, its anterior part shovel- and not hammer-shaped, the outer posterior 

 margins of the shovel sloping a little rearward with broadly rounded outer corners; 

 the breadth of shovel at eyes about 2.5 times as great as its length in front of mouth 

 in small specimens but nearly 3 times that great in large, 1.3 to 1.6 times as great as 

 its length at outer ends of nostrils" and a little shorter than head to origin of pectorals; 

 anterior contour of head an uninterrupted curve from eye to eye, without definite depres- 

 sions opposite nostrils and merely a slight concavity or sinuosity median to the latter in 

 some cases only, the midsector a little more ovate in adult males where length in front of 

 mouth is almost % as great as distance between nostrils, while in adult females or in young 

 of both sexes it averages less than % (almost 57%) ; a faintly marked groove runs for- 

 ward from nostril along anterior margin of head in some small specimens for a distance 

 about as great as distance from nostril to eye, but this is hardly visible or wholly obsolete 

 in larger specimens; distance from outer end of nostril to anterior edge of eye a little 

 greater than diameter of latter; a line connecting inner ends of nostrils passes anterior to 

 mouth by a distance about 1V2 times the diameter of eye, one connecting the centers 

 of eyes passes about through front of mouth, while one connecting the outer posterior 

 corners of shovel passes posterior to corners of mouth by a distance about equal to diameter 

 of eye. Rostral cartilage without median hole, but preorbital process with a strongly marked 

 inwardly directed spur on anterior margin. Large and small mucous pores on lower surface 

 of anterior part of head distributed in diffuse pattern. Diameter of eye ^/i to Vs as long as 

 length of head in front of mouth. Gill openings extending ventrally and almost evenly 

 spaced, the ist almost 1.5 times as long as diameter of eye or a little longer, the 5th almost 



16. The shovel of tiburo may average a little narrower relative to its length in northern specimens than in those 

 of the southern Atlantic. But the probability of local or racial variation is so great that recognition of this 

 difference does not seem essential in nomenclature. 



