514 DR. NEWELL ARBER AND MR. F. W. LAWFIELD ON THE 
external surface which two distinct species of Calamites possess in common. 
Similarly it is regarded as probable that Calamophloios Goepperti as here 
defined is common to at least two types of pith east, Calamitina approaimata 
Brongn. (= C. Schiitzeiformis, Kidst. & Jong. forma waldenburgensis, Kidst. 
& Jong.*) and Calumitina varians, Sternb., but that it possibly does not 
include all the pith casts known under the latter name. Likewise all pith 
casts of the Hucalamites cruciatus type probably did not have the corre- 
sponding external features characteristic of Calamophloios congenius as here 
defined. 
The problem is thus not so simple as it looks, and some elasticity in the 
nomenclature is necessary if it is to represent the known facts. 
In general we have attempted to avoid adopting new specific names for 
the types of Calamophloios as compared with the pith casts, except where 
we know or suspect that stereotyping is markedly in evidence—as regards 
the external features. At the same time we think it possible that eventually 
a set of specific names entirely distinct from those of pith casts may be 
found necessary. 
It may also be pointed out here, that a small difficulty arises as regards the 
nomenclature of species, if the same specific name is used for both types of 
preservation, Thus while a pith cast may be correctly designated as 
Calamitina undulatus (Brongn.), to call the corresponding external surface 
Calamophloios undulatus (Brongn.) would hardly be, strictly speaking, 
accurate, for there is no reason to believe that Brongniart himself knew of 
the external surface but only of the pith cast of this fossil. Strictly 
speaking it should be Calamophloios undulatus (Goode), since that observer 
first figured and described the external surface of this fossil. As, however, 
this method or that of supplying an entirely new name for each type (other 
than a pith cast) would tend to confusion on the one hand or a multiplicity 
of specific terms on the other, it seems, for the present at any rate, to be 
advisable where possible to retain the same specific name for both pith cast 
and its corresponding external surface. If the name of the authority in 
brackets after the species is taken to imply not merely a displacement of the 
genus but a definite emendation (which might, but need not, be written 
emend.), the system can perhaps stand, 
With regard to the term Calamophloios itself it may be necessary to add 
a few words. A similar genus Calamodendrojloyos has already been used 
both by Grand’ Eury f and Renault { in much the same sense as Calamo- 
phloios here, though with a more limited application relating only to the 
* Kidston & Jongmans (1915) p. 101. 
T Grand’ Eury (1877) p. 293. 
1 Renault & Zeiller (1888) p. 462. 
