Fishes of the Western North Atlantic 



473 



mature specimens yet seen were much smaller, as stated above. New Jersey specimens 

 weighed in recent years have ranged from 25 to about 70 pounds. 3' 



Developmental Stages. Embryos in late stages of development have the tail spine 

 (embedded in the skin) and resemble their parents closely in general appearance except 

 for somewhat longer tails. The earliest formed teeth, lost before birth or shortly there- 

 after, are round, loosely spaced, in eight or nine series in 1—3 irregular rows; those 

 formed subsequently, when the embryo is about 220— 250 mm broad, are in close 



Figure 108. Rhinoptera bonastis. A Upper teeth (above) with front row uppermost, and lower teeth (below) 

 with front row lowermost, from head of specimen about 1,500 mm wide (estimated), from Rio de Janeiro, 

 Brazil (Harv. Mus. Comp. ZooL, No. 535), about o.yx. B Upper teeth (above) with front row uppermost, 

 and lower teeth (below) with front row lowermost, of male, 567 mm wide, from Newport, Rhode Island, with 

 eight series below (Harv. Mus. Comp. Zool., No. 746), about I X . C Cross sections of upper dental plate 

 (above) and of lower dental plate (below) of same, to show curvature. 



mosaic from their earliest appearance and are normally in seven series. The unborn 

 young lie in the uteri in pairs, rolled together head to tail. Six have been found in one 

 female, while another gave premature birth to two on capture. 



Habits. This Cow-nosed Ray (and probably all members of its genus) feeds chiefly 

 on hard-shelled mollusks, both bivalve and univalve, which it crushes between its power- 

 ful dental plates, discarding the broken shells. Razor clams {Ensis), oysters, and clams 

 are the chief diet of those that visit North Carolina waters, while the few that reach 

 southern New England feed on clams, ^^ large gastropods, lobsters, and crabs. It appears 



37. Fowler, Fish Culturist, 6, 1927: 11;; 7, 1928: 225. 



38. There is at least one recorded instance of a Cow-nosed Ray being caught on a hook baited with a clam on the New 

 Jersey Coast; see Fowler (Proc. Acad. nat. Sci. Philad., 6g, 1917: 109). 



