Fishes of the Western North Atlantic 505 



Teeth ^\°l^^l^^^g -, widely unlike in the 2 jaws; upper teeth thorn-like, on broad 

 bifid bases, curved rearward, erect toward center of mouth but moderately oblique toward 

 corners, the ist tooth small; lower teeth blade-like, with quadrate bases and broad- 

 triangular cusps, the latter with regularly serrate edges, erect toward center of mouth, 

 but oblique and decreasing in size toward corners to a degree apparently depending on 

 age and perhaps on individual variation; the median lower tooth as large as others, 

 symmetrical, weakly notched on both edges at junction of cusp with base and overlapping 

 its neighbor basally on either hand, the lateral lower teeth notched only on outer side and 

 each overlapping the next outermost tooth; 3 or 4 series functional in upper jaw, and i or 

 2 series functional in lower jaw, depending on the stage in replacement. 



First dorsal only about % as long at base as head, brush-shaped with broadly 

 rounded apex, its posterior margin nearly straight and perpendicular, its free rear corner, 

 or free lower margin, about as long as base, Its origin posterior to tips of pectorals by a 

 distance about as long as horizontal diameter of eye when pectorals are laid back. Second 

 dorsal a little larger than ist, its origin about over middle of bases of pelvics, its distal 

 margin concave and rear corner acute, thus differing from ist dorsal, its free rear tip about 

 as long as its base. Interspace between 2nd dorsal and caudal a little more than i V2 times as 

 long as base of 2nd dorsal. Caudal a little more than Vs of total length, obliquely truncate 

 terminally with broadly rounded apex, its lower margin deeply incised subterminally in 

 rectangular outline and thus sharply marking off the terminal sector, its lower anterior 

 corner rounded, about a right angle, the lower anterior margin a little less than V2 as long 

 as upper margin. Pelvics about i Y^ times as long at base as 2nd dorsal, with nearly straight 

 margins, broadly rounded apices and tapering rear corners. Pectoral about % as long as 

 head, paddle-shaped, with very broadly rounded tip, weakly convex outer margin and 

 more strongly convex distal margin, the transition from distal to inner margin gradual, 

 there being no definite inner corner. 



Color. After preservation, uniformly dark chocolate or cinnamon brown below as 

 well as above; also described as sometimes violet brown with poorly defined blackish spots 

 in life, the fins with pale or whitish margins and caudal black-tipped. 



Size. The young are born at a length of approximately 300 mm., but most of those 

 caught are between 1,000 and 1,500 mm. (40 to 60 inches) long; the longest of which we 

 have found definite measurement was 1,820 mm. (72 inches)." A specimen of about five 

 feet weighed about 23^/'2 pounds gutted."^ Females are larger than males, as is commonly 

 the case among sharks. 



Developmental Stages. Development is ovoviviparous. Gravid females are reported 

 as containing 10 to 16 young. An embryo of 270 mm., still with the large yolk sac, already 

 shows all the diagnostic characters of the adult except for the teeth, denticles and rela- 

 tively larger eyes (horizontal diameter about % as long as snout in front of mouth). ^^ 



11. Dumeril, Hist. Nat. Poiss., /, 1865: 452. 



iia. Nichols and Firth, Proc. biol. Soc. Wash., 52, 1939: 85. 



12. For account of the uterine wall of a gravid female, see Ranzi (Publ. Staz. zool. Napoli, /j, 1934: 366). 



