226 EXPLANATION OE THE PLATES. 



PLATE III. 



Fig. 1. Posterior part of inferior surface of skull of Loxomma, a different 

 specimen from that shown in Plates I. and II. Natural size. R, 

 ridge on median line, fractured ; P.n.o, posterior nasal orifice ; 'B.sph, 

 basisphenoid ; B.oc, basioccipital ; Ar.cav, situation of articular ca- 

 vity, here broken away ; F.m, foramen magnum, edge of ; F.exoc, 

 facets of exoccipitals ; Qu, quadrate bone ; Mast, mastoid bone ; 

 Pter, pteiygoid bone. 



Fig. 2. External surface of right half-mandible of Loxomma, supposed to 

 be of the same specimen as is figured in Plates I. and II. Half natural 

 size. The fractured part, the external end of the articular cavity, 

 and the marginal groove along the lower border are well shown. 



Fig. 3. Internal surface of fragment of left half-mandible, showing the 

 symphysis, the difference of level between the alveolar borders, the 

 teeth, and the interdental depressions. Half the natural size. 



Fig. 4. Dorsal vertebra, natural size. C, centrum ; N.c, neural canal ; 

 S.p, spinous process; T.p, transverse process; A.z, anterior zygo- 

 matic process ; P.z, posterior zygomatic process. 



PLATE IV. 



Fig. 1. Rib, half the natural size. 



Fig. 2. Longitudinal antero-posterior section through middle of a small 

 tooth and its alveolar border, from right half-mandible, magnified 

 four diameters. A, alveolus; E, enamel; D, dentine; P, pulp- 

 cavity. 



Fig. 3. Transverse section near apex of tooth, as indicated in fig. 2, sec. 3. 

 Magnified 16 diameters. E, enamel ; D, dentine ; P, pulp-cavity. 



Fig. 4. Transverse section just above the cessation of the plicae, magnified 

 16 diameters. See fig. 2, sec. 4. E, enamel ; D, dentine ; P, pulp- 

 cavity. 



Fig. 5. Transverse section immediately below alveolar border, fig. 2, sec. 5. 

 Magnified 16 diameters. D, dentine; P. pulp-cavity; p, radiations 

 from pulp-cavity ; t, toothlets ; B, bone. 



Fig. 6. Portion of fig. 5, to show minute structure. Magnified about 48 

 diameters. B, bone ; ex J, external layer of dentine ; gr.l, granu- 

 lar layer ; D, dentine, tubular ; pi, plicae, long and short ; ex. in, ex- 

 ternal layer infolded ; gr.in, granular layer infolded, 



