§ 22. 



CLATHRARIA LYELLII. 395 



and in the clays of Germany,* many specimens of the stems 

 of a very curious plant, formerly supposed to be related to 

 the Euphorbia, or Cacti, have been discovered. These 

 stems are of various forms ; some are cylindrical, and 

 tapering at both ends ; others are flattened, and of a cla- 

 vated shape. The constituent substance is a grey, compact, 

 subcrystalline sandstone, and the external surface of the 

 stems is traversed by fine meandering grooves, and deep 

 tubular furrows, lined with minute quartz crystals ; a trans- 

 verse section exhibits the surface covered by small pores, 

 and a few large openings, the sections of the tubes. In a 

 specimen which I picked up on the beach at Brook Point, 

 bundles of vascular tissue are preserved ; these are disposed 

 in a flexuous zone round the margin of the stem. The 

 plant is supposed by Dr. Brown to be allied to the Cycadeae.f 

 Cones and stems of a species of Zamia have been found with 

 bones of the Iguanodon in Sandown Bay .J 



22. Clathraria Lyellii (Ligns. 92, 93). — The most 

 interesting plant belonging to this tribe of coniferaa, of 

 which any vestiges have been found in the Wealden, is 

 that first discovered by me in Sussex, and described under 

 the name of Clathraria Lyellii. § 



The fossil remains consist of portions of the stem, scored 

 by the imprints left by the attachment of the petioles ; leaf- 

 stalks ; the internal axis ; and obscure indications of the 

 foliage and seeds. || The stem is composed of an axis, having 

 the surface covered with reticulated fibres; and of a false bark, 

 produced by the union of the consolidated bases of the pe- 

 tioles, the insertions of which are rhomboidal and transverse. 



* Mem. Nord. Weald. Tab. III. 

 f See Geology of the Isle of AYight, p. 288. 

 + Medals of Creation, vol. i. p. 160. 



§ Fossils of Tilgate Forest, PI. I. II. and III. and Geol. of the S. E. 

 of England, PI. I. 



|| Medals of Creation, vol. i. p. 182. 



