Sphyroma harracuda; its Morphology, Habits, and History. 63 



Closely set in palisade fashion, beginning about opposite the space 

 between the first and second great fangs, are the small knife-like 

 teeth of the premaxillaries. These teeth, 

 pointing slightly' backward and extending 

 clear to the angle of the mouth, give the 

 upper jaw a very saw-like appearance, as 

 may be seen in figure 8, plate iii. The 

 data tabulated herewith would seem to 

 show that the number of these teeth is 

 fairly constant, the discrepancies being chiefly due to teeth broken 

 off and not yet replaced. 



An interesting point was passed over in the dried heads and seen 

 only when the fresh head was dissected— that the teeth of the lower 

 jaw, those of the premaxillaries, those on the palatines, and even the 

 great fangs under the snout; all the teeth in the mouth, except the 

 solitary fang of the lower jaw, are set "overlapping." That is, in 

 every case, where the teeth are crowded, the front edge of every tooth 

 rests on the outer side of the tooth before it, and its hinder edge is 

 set on the inside of the tooth behind it ; going from behind forward, the 

 teeth over-lap like the shingles on a roof. This is especially apparent 

 where new teeth are ready to erupt. Reference to figures 12 and 13 on 

 plate IV, photographs of the cleaned-ofT jaws, will make this plain. 



When the mouth is closed, the parts of this formidable dental appa- 

 ratus are approximated sausage-mill fashion, as follows: The teeth 

 of the lower jaw fit into deep grooves between the premaxillaries and 

 palatines of the upper jaw and the big anterior canine fits into the 

 pocket of the upper jaw which has already been described; the pre- 

 maxillary teeth of the upper jaw come to rest against the lip-like 

 membrane lying just outside the great teeth of the lower jaw, while 

 the huge palatines fit into a wide, deep space between the lower jaw 

 and the tongue, and finally the big anterior canines are received into 

 special recesses in the membrane lining the anterior part of the floor 

 of the mouth just behind the symphysis of the mandibles. Held in 

 such teeth no fish can escape save by leaving part of itself behind. 



The sausage-mill approximation of these teeth will be clearer after 

 an examination of figures 6, plate ii; 12, plate iv; 9 and 10, plate iii. 

 The particular point to be noted is the presence of the mandibular 

 breathing valve, and in its forward part the depressions in it which 

 accommodate the great canines of the upper jaw. However, the 

 modification of the mouth parts to fit these huge teeth does not 

 end here, but extends to the very bones themselves. In figure 13, 

 plate IV, the reader will discern on the inside of each ramus of the 

 lower jaw just behind the junction an excavation in the bone. These 

 are to receive the points of the great canines of the upper jaw. 



