ON FOSSIL FISH-TEETH. 301 



ent little pits or depressions, arising partly from some slightly irregular 

 wear of the surface. The outer and nearly vertical edges of the teeth 

 present a highly enamelled and polished surface, crossed longitudinally 

 by numerous striae, or slight ridges of growth. The edges of the late- 

 ral horns or spurs are marked by two or three sharp tooth like serrations 

 or projecting points, formed by these ridges. — (^Fig. 1,P1. xvi.. Figs. 1 

 and 5, PI. xiv.) 



The flat, or lower-jaw tooth of the same species (Figs. 4 and 5. 

 PL xiv^ is very different in outline. Seen in profile, the upper surface is 

 nearly flat, and parallel with the lower surface of the enamel layer, the 

 very marked and prominent ridges of the tooth projecting above the ge- 

 neral level. Of the total thickness of the tooth, two thirds at least be-~ 

 long to the enamel layer, the osseous layer being very thin. The ridges 

 or horns become regularly more marked and prominent from the front of 

 the tooth backwards to the centre or fourth ridge which is the most 

 prominent. The first or anterior horn is in this tooth marked by a slight- 

 ly convex rise along the middle of its upper surface, corresponding to, and 

 fitting into the slight depi'ession or furrow mentioned as being on the 

 corresponding anterior horn of the upper-jaw tooth. The other projec- 

 tions are sharply ridged and prominent. 



The general outline of these teeth is not so triangular as that of the 

 upper corresponding teeth. Tlie inner edges are less curved, and meet 

 at a more obtuse angle: the line joining the ends of its projecting horns 

 or spurs, would also be much curved, and not as in the corresponding 

 upper teeth, nearly straight. The worn surface of the tootli is ex- 

 actly similar to that of the upper teeth, the whole being finely punc- 

 tulated, and having also numerous little irregular pits or depressions. 

 The same bright enamelled surface crossed by numerous strije of growth 

 shews on the sides of the tooth. Projecting from the bony surface of 

 the tooth below, there is a small projecting process for the attachment 

 of the muscles giving motion to the tooth (Figs. 4 and 6, PL xiv.) The 



