554 
MR. TOMES ON THE STRUCTURE OF 
fluent laminae of obliquely placed enamel fibres, which have a diameter of about the 
5000th of an inch, while the layers have a thickness of from the 1362nd to the 2150th 
of an inch, and leave the dentine at an angle of 65°. In the outer division of this 
tissue the fibres lie at an angle of 35° with the surface of the dentine. 
Prof. Owen describes the structure of the teeth of the Agouti from a longitudinal 
section of an upper incisor, and says, “ The fibres composing the inner and more 
opake part of the enamel proceed obliquely, but almost transversely across that 
substance, with a gentle curve in the opposite direction to the last curve of the con- 
tiguous dentinal tubes, viz. with the convexity towards the crown : the fibres of the 
peripheral layer of the enamel make a slight bend towards the crown ; these enamel 
fibres are as thick as two of the dentinal tubes with their interspaces ; their ends are 
lost in the clear peripheral substance to which the distinct, apparently structureless 
brown layer of cement is attached, and to which the colour of the convex surface of 
the incisor is due*.” 
Had Prof, Owen made transverse sections of this tooth, he would I think have been 
led to give a wholly dilferent account of the enamel ; he would have seen the waved 
appearance which closely corresponds with that I have described in the incisor teeth 
of the Porcupine, and is produced by a similar flexuous arrangement of the component 
fibres ; he would also have seen that the brown colour is resident in, and is due to a 
stain in the terminal ends of the enamel fibres. The enamel of the molar teeth of 
this animal resembles that of the corresponding teeth of the Porcupine. 
Dasyprocta Acouchy (Erxl.). The dental tissues of this creature closely resemble 
those of the preceding species. 
Coelogenys Paca (Schreb.). — The dentine of the incisor teeth does not differ very 
perceptibly from that of the corresponding teeth of the Agouti and Porcupine. It 
measures about the 5th of an inch, while the larnelliform portion of the enamel is 
about the 107th, and the fibrous 300th of an inch in thickness. In a longitudinal 
section the confluent layers of enamel fibres leave the dentine at an angle of 70°, 
and the fibres in the outer fibrous part of the tissue lie at an angle of 40°, The layers 
have a thickness of from the 1000th to the 1667th of an inch ; and the fibres are 
about the 5000th of an inch in diameter. In an oblique transverse section the waves 
of the enamel fibres are more strongly marked than in the enamel of the Porcupine, 
as shown in fig. 38. 
An oblique longitudinal section shows with great distinctness alternate layers of 
fibres divided more or less transversely, and intermediate ones pursuing an oblique 
course. Fig. 37 illustrates faithfully this strongly-marked and peculiar appearance. 
Capromys Fournieri (Desm.). — The dentine terminates at the enamel without the 
presence of oblique elongated cells, but small rounded cells are present and inter- 
mingled with the terminal anastomosing branches of the dentinal tubes. The dentine 
of a lower incisor measures about the-g^th, the larnelliform portion of the enamel the 
* Odontography, page 404. 
