114 Memoir Sears Foundation for Marine Research 



pits both strongly developed as transverse furrows, straight or only slightly curved, with 

 convexities directed rearward, the lower pit a little in advance of the upper. Dermal den- 

 ticles so small and flat that the skin is velvety to the touch, each a little broader than long, 

 with 3 teeth, the median a little longer than others, and a corresponding number of low, 

 sharp-topped ridges, separated by broad valleys 5 pedicels moderately long, on broad bases. 

 Head and snout conical, the length of head to pectoral a little less than V^ of total 

 length. Snout pointed, its length in front of mouth about Y^ of head to origin of pectorals. 

 Eye circular, its diameter about 30% as long as snout in front of mouth. Spiracles lacking 

 in specimens studied but described as sometimes present as minute pores behind eyes. First 

 gill opening slightly longest, about as long as snout in front of eye, the lower end of 5th 

 curving rearward and ventrad for a short distance around origin of pectoral, the space 

 between 4th and 5th only about V2 that between ist and 2nd, the 5th more oblique than 

 others. Nostrils approximately transverse, hardly Vs as long as distance between them, 

 their inner corners about ^/4 as far from mouth as from tip of snout, the anterior margin 

 with a low rounded lobe (Fig. 16 B). Mouth broadly rounded, about lYo times as broad 

 as high (thus somewhat shorter, relatively, than in oxyrinchus). Upper labial furrow 

 about 0.3 as long, the lower 0.2 as long, as distance to symphysis of the respective jaws, the 

 upper partly, and the lower almost entirely, concealed when mouth is closed. 



^^V^^^^^ffW^ 



Figure 16. Lamna rtasus. A Lower view of head of young male from specimen shown in Fig. 15. B Right-hand 

 nostril, about 2.5 x. C Dermal denticles — -general view, about 40 x; apical view, about 80 x. D Upper and 

 lower teeth of a larger specimen from Platts Bank, Gulf of Maine, about 1.3 x. 



