74 DR. D. H. SCOTT ON THE HETERANGIUMS 
Leaf-trace consisting of two bundles where it leaves the stele, dividing 
into four in the cortex. Four bundles in the petiole. Number of traces in 
the transverse section from two to four. Traces traversing the stem for a 
long distance before passing out. 
Locality. Halifax Hard Bed, Lower Coal Measures. 
Hereraneium Lomaxin, Will. in MS. 
Williamson, in his 17th Memoir (1890, p. 96), states, under the heading 
Heterangium Grievii, that Mr. Lomax had found specimens of the same plant 
from Dulesgate in Lancashire. He proceeds: * But along with these he 
brought from the same locality a series of sections of what at first seemed to 
be a different species of Heterangium. But long and careful comparison of 
all the examples of that genus in my cabinet convinced me that the supposed 
new forms were merely the H. Grievii in a younger state of growth.” 
The specimens figured and shortly described in the memoir referred to 
are those in the “younger state of growth” (Williamson, l. e. pls. 14, 15. 
figs. 14-18), whieh Williamson at first regarded as distinct. He did not 
deseribe the other, more advanced form, which he had always considered as 
simply H. Grierü. In the joint memoir (Williamson & Scott, 1895) the 
Dulesgate forms are only referred to incidentally, but both the younger and 
more advanced conditions are illustrated for special points (l. c. pl. 26. fig. 21; 
pl. 27. figs. 28, 29). It was no doubt to the younger and more peculiar 
form that Williamson's unpublished MS. name of H. Lomaati was intended 
to apply. In the joint memoir we also described and figured “a Heterangium 
of uncertain species," from Dulesgate, and provisionally named it H. cylin- 
dricum (l. c. p. 164, pl. 28. figs. 30, 31). 
There are therefore three forms of the Dulesgate Heterangiums which 
have already been recorded. 
1. The young stems with little or no secondary thickening. This form 
will be called « (Pl. 4. figs. 16, 17). 
2. The older stems, with well-marked secondary tissues, resembling 
H. Grievii, now to be called the 8 form (Pl. 2. Phots. 9, 11, 12, 13). 
3. The so-called //eterangium cylindricum™ (Pl. 2. Phot. 14). 
After careful comparison of all available sections I have come to the con- 
clusion that all the above, including one or two minor variants, belong to one 
species (of course, quite distinct from the Lower Carboniferous H. G'rievii), 
to which the name //. Lomazii is collectively applied. The only Dulesgate 
* All the specimens of these three forms appear to have come from one coal-ball. This is 
Mr. Lomax's recollection, and it is confirmed by the uniform character of the matrix in which 
the stems are imbedded. The single specimen of Heterangium minimum (see below) came 
from a different block. It is remarkable that no new specimens of H. Lom«xii have been 
met with since the original discovery by Mr. Lomax about 1890. The species must have 
been very rare or the conditions for its preservation very unfavourable. 
