1852.] LYELL — BELGIAN TERTIARY FORMATIONS. 369 



EXPLANATION OF PLATES XVIL XVIIL XIX. & XX 



Plate XVIL 



Fig. 1. Map of part of Belgium and French Flanders. 

 Fig. 2.-) 



Fig. 3. > Portions of the same, on enlarged scales. 

 Fig. 4. J 



Plate XVIIL 



Fig. I a,lbflc. Echinolampas Galeottianus, E. Forbes, nat. size. 



Fig. 2 a, 2 b, 2 c. Dekini, Galeotii, sp., nat. size. 



Fig. 3 a, 3 A, 3 e. Nucleohtes approximatus, Galeotii, nat. size. 

 Fig. 4 a, 4 i, 4 c. Echinocyamus propinquus, Galeotii, magnified 

 Fig. 5 a, 5 i, 5 c. Scutellina rotunda, Galeotii, sp., magnified. 

 Fig. 6 a, 6 5, 6 c. Lenita patelloides, Galeotii, sp., magnified. 

 Fig. 7 a, 7 b. Spatangus Omalii, Galeotii, nat. size. 

 Fig. 8. Crania Hoeninghausii, Micheloiii, magnified. 



Plate XIX. 



Fig. 1. Nipadites Burtini, Brongniart, sp. 



Fig. 2. , , abortive fruit. 



Fig. 3. lanceolatus, Bowerbank : a, the pericarp ; b, the nucleus or cast, 



representing the nut. 



Fig. 4. , nucleus, seen edgewise. 



Fig. 5. Parkinsonsis, Brongniart, sp. : a, pericarp ; b, nucleus. 



Fig. 6. , nucleus : a, position of the opening at the base 



where the sand entered. 



The figures are all ^ nat. size. 



Plate XX. 



Fig. 1 . Honium BruxelUense, Lgell, nat. size. 



Fig. 2. , , another specimen, nat. size. 



Fig. 3. Portion of the surface of fig. 2, near the centre and to the left of the ridge, 



showing the reticulated structure. Magnified 12 diam. 

 Fig. 4. Portion of surface of fig. 2, a little below the centre, and including a part 



of the rough or granulated ridge : a, reticulations running obliquely 



downwards towards the ridge, b. Magnified 12 diam. 

 Fig. 5 a. Portion of surface of fig. 2, from the margin close to and on the right 



(as seen in the figure) of the peduncle, showing the reticulation on the 



rounded margin of the cast, and the smooth narrow cavity or sulcus 



formerly occupied by the blunt edge of the Honium. Magnified 12 



diam. 

 Fig. 5 b. Portion of surface of fig. 2, from the sinus ; the reticulation assmnes 



the aspect of a wrinkled membrane. Magnified 12 diam. 

 Fig. 6 a, 6 b. Spines from the surface of fig. 1 : a, c, c, sponge spicules ; b, b, d, 



spines of Echinoderms. Magnified. 

 Fig. 7. Nipadites Burtini. Brongniart, sp., having the husk bored by Teredinse : 



a, position of aperture at the base into which the sand has entered. 



^ nat. size. 

 Fig. 8. , , base of the same specimen : a, nucleus or 



cast of the endocarp ; b, position of aperture. \ nat. size. 



