12 



DESCRIPTION OF THE PLATES. 



smaller ones in the interspaces, with the 

 bases of two of the larger teeth showing 

 the convergence of the peripheral fissures 

 towards the centre of the tooth. The 

 end view of the section shows the alveolar 

 groove and its outer parapet. Fig. 2. 

 Parts of the lower jaw of a fossil Sauroid 

 (Holoptychius Hibbertii, Agas. Rhizodus 

 mihi) : a, implanted and anchylosed base 

 of one of the large teeth. Original. 



PLATE 36. 



One of the large laniary teeth of the 

 natural size, with a longitudinal sec- 

 tion removed from the base, and a mag- 

 nified view of the section : Rhizodus Hib- 

 bertii, Original. (A transverse section 

 shows the radiations of the divisions of 

 the pulp-cavity continued into the cylin- 

 drical processes of the base of the tooth, 

 according to the labyrinthic type of struc- 

 ture.) 



PLATE 37. 



A portion of a transverse section of the 

 crown of one of the large laniary teeth 

 of Rhizodus Hibbertii. These teeth and 

 the analogous ones of the recent Sau- 

 roid fishes differ from the teeth of the 

 Labyrinthodon in the larger proportion of 

 the crown in which the pulp cavity is 

 simple, as in the figure. Original. 



PLATE 38. 



Fig. 1. — Lower jaw and dental masses 

 of the Globe- Fish (Diodon Hystrix). 

 Fig. 2. Portion of the same cleft 

 vertically near the symphysis ; a, the 

 last formed plates of the posterior tooth : 

 b, the same of the anterior tooth : c, 

 the intervening vascular canal. Fig. 3. 

 A portion of a section of the posterior 

 tooth magnified 600 linear diameters : a, 



intervening layer of osseous or cemental 

 substance ; between b and c the dentinal 

 layers of the compound tooth. Original. 



PLATE 39. 



Fig. 1. Jaws of the Tetrodon lineatus : a, 

 posterior lamelliform teeth of upper 

 jaw. Fig. 2. Portion of a vertical sec- 

 tion of the posterior tooth of Diodon 

 Hystrix magnified 1 20 linear diameters. 



PLATE 40. 



Fig. 1. — Side view of intermaxillary and 

 mandibular teeth of a File-Fish (Balistes 

 forcipatus). Fig. 2. a, upper, b, lower 

 pharyngeal bones and teeth, left side, of 

 Balistes forcipatus. Fig. 3. Outside 

 view of right intermaxillary, showing 

 the alveoli for the union by double gom- 

 phosis of the outer teeth. Fig. 4. Inside 

 view of the same, showing the inner 

 teeth. Fig. 5. Successional intermaxil- 

 lary teeth exposed : a, osseous tubercle 

 which supported the tooth in place : b, 

 the end of the successional tooth which 

 has caused the absorption of the osseous 

 tubercle of the second intermaxillary 

 tooth. Fig. 6. Successional teeth of the 

 inner row exposed. Fig. 7. Inner sur- 

 face of teeth of the lower jaw. Original. 



PLATE 41. 



Fig. 1. — Upper and lower jaws and teeth 

 of a Sea-Bream (JDentex Argyrozona), 

 Fig. 2. Inside view of those of the left 

 side : a, intermaxillary : b, maxillary : 

 c, dentary : d, articular. 



PLATE 42. 



Fig. 1. — Upper view of the teeth of the 

 lower jaw of Sargus rufescens. Fig. 2. 

 Front view of incisors of a young Sargus 



