Fishes of the Wester ti North Atlantic 245 



toral as to the origin of the pelvics; from fasciatus by the shape of the teeth (cf. Fig. 42 D 

 with 43 A), by its lobed lower caudal, and by its plain coloration 5 from mento^ by a much 

 larger eye relative to the gill openings (the horizontal diameter of its eye being about as 

 long as the third gill opening but only about 60% as long in mento), by the distance be- 

 tween its nostrils which is at least approximately half as great as the width of the mouth 

 (considerably less than Y^ that great in mento), by a relatively smaller pectoral with inner 

 margin only about 1.3 times as long as snout (1.8 times as long in mento), by its more 

 strongly sculptured and more opaque denticles (cf. Fig. 42 E with 42 I) and by the shapes 

 of its teeth (cf. Fig. 42 D with 42 J). Adults of canis are plain colored also, whereas those 

 of mento often are white-spotted (p. 260). 



Descriftion. Proportional dimensions in per cent of total length. Male, 781 mm., 

 from Buzzards Bay, Mass. (Harv. Mus. Comp. Zool., No. 35245). Female, 1,231 mm., 

 same locality. 



Trunk at origin of -pectoral: breadth lO.O, 10.35 height 9.9, lO.i. 



Snout length in front of: outer nostrils 3.8, 3.2; mouth 6.4, 5.4. 



Eye: horizontal diameter 2.8, 2.3. 



Mouth: breadth 5.5, S-5'i height 2.7, 2.3. 



Nostrils: distance between inner ends 2.9, 2.6. 



Labial furrow length: up-per 2.0, 1.9; lower 1.5, 1.4. 



Gill opening lengths: ist 2.2, 2.75 2nd 2.4, 2.8; 3rd 2.6, 3.2; 4th 2.6, 3.2; 5th 



2.0, 2.4. 



First dorsal fin: venkzi height 9.5, 8.3; length of base ii.i, 12.3. 



Second dorsal fin: vertical height 6.8, 6.7; length of base 8.9, 10.6. 



Anal fin: vertical height 3.6, 4.2; length of base 5.4, 5.5. 



Caudal fin: upper margin 21.2, 18.8; lower anterior margin 8.7, 7.0. 



Pectoral fin: outer margin 13.6, 13.9; inner margin 7.4, 6.7; distal margin 12.4, 



12.5. 



Distance from snout to: ist dorsal 26.8, 28.6; 2nd dorsal 59.7, 61.7; upper caudal 



78.8, 81. 2j pectoral 18. i, 19.1; pelvics 41.5, 47.6; anal 64.3, 68.0. 



Interspace between: ist and 2nd dorsals 22.0, 22.0; 2nd dorsal and caudal 10.5, 



9.5 ; anal and caudal 6.8, 6.7. 



Distance frotn origin to origin of: pectoral and pelvics 24.3, 29.2; pelvics and 



anal 22.4, 19.8. 



Trunk slender and tapering rearward, its height at origin of ist dorsal about ^i its 

 length to origin of caudal, the midline of the back with a low but sharp-edged and unmis- 

 takable dermal ridge running rearward from about opposite the ist or 2nd gill opening 

 nearly to the origin of the caudal. Trunk sector to cloaca a little shorter than tail sector. 

 Caudal peduncle subcylindrical, without lateral ridges or precaudal pit either above or 

 below. Dermal denticles irregularly spaced, sometimes overlapping but sometimes with 



6. Mento may occur in Argentine waters, see p. 260. 



