262 ORIGINAL ARTICLES. 
etc. One species of Dendrobium , D. normale, derives its specific name 
from this circumstance. Dr. Lindley remarks, that in cultivation 
Cal ant he veratrifolia occasionally produces regular flowers.* 
M. Gris has placed on record some interesting cases of regular 
Peloria, affecting the flowers of Zingiber Zerumbet.-f 
The two forms of Peloria, which I have thus attempted to illus¬ 
trate, present many points of great interest for the systematic, no 
less than for the philosophic botanist. They afford many subjects for 
extended investigation, and give rise to much, not wholly unprofitable, 
speculation. It would be interesting to determine, if possible, the 
effect of relative position and other external circumstances in pro¬ 
ducing one or the other form of Peloria; to ascertain whether this 
dimorphism has any relation to increased or diminished fertility, or 
to any other functional changes; to discover which of the two forms 
is the more constant; which is to be referred to exaltation of, and 
which to degeneration from, the characteristics of an assumed type 
or possible progenitor; and to trace the numerous gradational forms 
existing between the two kinds in the same species, as well as those 
between distinct, or so-called distinct, genera and families. 
Into these topics I must not now enter. 
XXIV.—On the Dossil Estherl#:. By T. Rupert Jones, D.G.S., 
Professor of Geology and Mineralogy, Royal Military College, 
Sandhurst. 
Geologists, looking at fossils as witnesses of the varied condi¬ 
tions of land and water in remote times, desire to inquire fully into 
the probable habits and relationship of every organic relic of the 
past. Dossil shells, forming the chief portion of the materials in the 
hands of the palaeontologist, become especially the subject of such 
inquiries, and are made to yield evidence as to the relative age and 
the mode of formation of the several strata in which they occur. It 
is by comparing the extinct shells with those now living, and assum¬ 
ing for the fossil mollusc habits similar to those belonging to the 
most nearly allied of its existing congeners, that geologists for the 
most part form a judgment as to the character of many strata, whether 
they were marine or fluviatile in their origin, whether formed in 
shallow or in deep water. We are not surprised that the evidence 
thus obtained should often be weak and occasionally faulty, seeing 
that mere similarity in the form of shells has sometimes to be taken 
as evidence of generic relationship or of specific identity; whereas the 
* Gard. Chron. 1854, p. 804. 
f Bull. Soc. Bot. Fr. Mai, 1859. 
