SCLERODERMS. 83 



tooth (PI. 40, figs. 3 and 5). The circumference of the base of the 

 fully formed tooth is attached by a shght anchylosis to the margin 

 of the alveolus, but the confluence of the tooth with the bone is much 

 less complete than in many other fishes. 



There would seem to be a constant and pretty quick succession of 

 these teeth, for in all the jaws of different species which I have ex- 

 amined, there were the crowns of a second or new series of teeth, 

 generally pretty far advanced in their development. The successors 

 of the external teeth of the right intermaxillary bone, exposed by re- 

 moving the outer wall of their alveoli, are represented in situ in fig. 5 

 of Plate 40 : (a) points to the osseous tubercle on which the tooth 

 about to be displaced was fixed ; the absorbent process has com- 

 menced at its apex : at (6) the corresponding bony tubercle has been 

 thus entirely removed, and the obtuse apex of the new tooth has 

 protruded in the socket of that which it has displaced. The cavi- 

 ties containing these teeth communicate with the exterior of the jaw 

 by foramina, situated as in most other fishes, on the outer side of the 

 base of the teeth in place (PL 40, figs. 1 and 3). 



The teeth of the posterior row, which are pecuHar to the upper 

 jaw, are six in number, three in each intermaxillary bone : 

 they present the form of elliptical plates, compressed laterally, 

 rounded at the base, and slightly pointed at the apex. The 

 anterior tooth is the largest, measuring in Balistes forcipatus six 

 lines in length, and three in breadth, but scarcely half a line in 

 thickness ; the two other teeth progressively diminish in size (PI. 40, 

 fig. 4). These posterior teeth lie in close juxtaposition with 

 the outer row, and like the posterior small upper incisors of the hare 

 and rabbit, receive part of the appulse of the inferior teeth. They 

 are affixed by a very oblique and slightly excavated base to a shallow 

 alveolus, having a convex rising of bone in its middle (PI. 40, fig. 6). 

 They are also deciduous, and the presence of well developed reserve- 

 teeth in cavities of the jaw, immediately internal to those of the ex- 

 terior row, would indicate that the succession of the teeth of the inner 

 row is likewise unlimited. The foramina leading to the cavities of the 

 successional teeth are seen immediately above the bases of the teeth 

 in place. The germs of the successors of the inner row of teeth ex- 



G 2 



