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 12and 13 on plate iv, photographs of the cleaned-off 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 12, plate iv; 9 and 10, plate 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.
There are no teeth on the vomer, but on the tongue is a number of rows of small, sharp-pointed recurved teeth which must materially aid in the swallowing process, as do the large number of small teeth covering the pharyngeals above and below and the inner edges of the gill-arches. These are quite necessary, since the great barracuda chops its prey (if of any size) into large fragments which are swallowed whole. In addition to the structures described, there is a large breath
ing valve in the upper jaw, just posterior to the four great canines and anterior to the palatine teeth. Below, a similar structure is found just in front of the tongue. The tongue has considerable freedom of motion.
On the under side of the lower jaw, just behind the point of junction of the mandibles, are two round apertures leading into blind sacs extending both backward and forward some little distance. What function these subserve is not known to the writer. They are shown in figure 6, plate Before leaving this subject it may be of interest to give the sizes of some of these great teeth. In fish No. 10 (3 feet 10 inches long), the single tooth at the apex of the lower jaw measures 13 mm., the big upper front teeth are 15 mm. long free of the gum, and the knife blade teeth implanted on the palatines run from 9 to 13 mm. The large teeth of specimen No. 12 (55 inches long), which is No. xv of the tables of teeth, have for the most part had their points broken off and hence their measurements, generally speaking, do not show up so large as they should. Thus the big lower tooth measures only 11 mm., while the upper ones run from 12 to 14 (tips broken) to 17 and 18 mm. (perfect teeth). The palatine teeth of this fish run from 9 to 16 mm. These measurements, it must be understood, are all made from dried specimens and may possibly be slightly greater than in the freshly caught fish. When the flesh was cleaned off of the fresh head, on the lower jaw the big anterior tooth (tip broken) measured 10 mm. and the great chopping teeth further back ran from 6 to 9 mm., aver aging about 7 to 8 mm. The great fangs of the anterior upper jaw measured 11, 13 (two teeth), and 14 mm. (Two other teeth were at the point of erupting.) The four great incisors on the right pala tine measured 12, 14, 8 (tip broken), and 10 mm. from before back ward. Similar measurements for the four corresponding teeth on the left palatine were 12, 11, 11, and 9 mm.
Figure 5, plate n, shows the number and relative position of these great teeth of the upper jaw. Some idea also can be gotten of the size, shape, and position of those of the lower jaw. The photograph was taken looking into the mouth from behind. The two inner groups of teeth are the great fangs on the premaxillaries. The outer groups are the huge knife-shaped teeth on the palatines.