trunk and scales, in our search for their distinguishing characters.
I have elsewhere (Geol. Trans. London, N. S. vol. ii. part iii. 1828) instituted a comparison between the internal structure of two species of these fossil trunks, and that of the trunks of a recent Zamia and recent Cycas.[1]
I must refer to the memoir, in which these sections are described, for specific details as to the varied proportions and numerical distribution of these concentric circles of laminated wood and cellular tissue, in the trunks of living and fossil species of Cycadeæ.{{#tag:ref|Plates 60, Fig. 1, and 61, Fig. 1, represent very perfect specimens of fossil Cycadites from Port land, now in the Oxford Museum: both having the important character of Buds protruding from the Axillæ of the leaf stalks.
The section given in Pl. 59, Fig. 2, of the trunk of a recent Zamia horrida, from the Cape of Good Hope, displays a structure similar to that in the section of the fossil Cycadites megalophyllus from the Isle of Portland; (Pl. 60, Fig. 2) each presents a single circle of radiating laminæ of woody fibre, B, placed between a central mass of cellular tissue, A, and an exterior circle of the same tissue, C. Around the trunk, thus constituted of three parts, is placed a case or false bark, D, composed of the persistent bases of fallen leaves, and of abortive scales. The continuation of the same structure is seen at the summit of the stem, Pl. 60, rig. 1, A. B. C. D.
The Cycadites microphyllus, Pl. 61, Fig. 1, affords a similar approach to the internal structure of the stem in the recent Cycas. The summit of this fossil exhibits a central mass of. cellular tissue (A,) surrounded by two circles of radiating woody plates, B. b., between these laminated circles, is a narrow circle of cellular tissue, whilst a broader circle of similar cellular tissue (C) is placed between the exterior laminated circle, (b) and the leaf scales (D.) This alternation of radiating circles of wood
- ↑ M. Ad. Brongniart has referred these two fossil species to a new genus, by the name of Mantellia nidiformis and Mantellia cylindrica; in my paper, just quoted, I applied to them the provisional name of Cycadeoidea megalophylla and Cycadeoidea microphylla; but Mr. Brown is of opinion, that until sufficient reasons are assigned for separating them from the genus Cycas or Zamia, the provisional name of Cycadites is more appropriate, as expressing the present state of our knowledge upon this subject. The name Mantellia is already applied by Parkinson (Introduction to Fossil Org. Rem. p. 53) to a genus of Zoophytes, which is figured in Goldfuss, T. vi. p. 14.,
