Dr. H. A. Nicholson on the Genus Climacograpsus. 377 
a. Base of the common form of C. teretiusculus, with a short radicle : Co- 
niston Mudstones. b. Base of the same, showing a long median radicle 
and two long lateral spines: Upper Llandeilo, Dobb's Linn, near Moffat. 
the same, showing the commencement of the radicle enve- 
loped in a sheath : Upper Llandeilo, Hart Fell, near Moffat. «d. Base 
of the same, showing the radicle swelling out below into a species 
of vesicular dilatation: Upper Llandeilo, Garple Linn, near Moffat. 
All much enlarged. 
rudimenta: A second peculiarity, first noticed by Mr. Car- 
ruthers (Intellectual Observer, June 1867), consists in the fact 
that whilst the filiform radicle may be prolonged for an inch 
or more below the body of the frond, its upper extremity is 
enclosed, for the space of a line or thereabouts, in a tubular 
Sheath derived from the proximal end of the frond (fig. 2 c). 
In the third variety (fig. 2d) the proximal extension of the 
axis is slender at its commencement close to the base of the 
frond, but gradually dilates into a long narrow vesicular body, 
which is elliptical or fusiform in shape, and may attain a 
length of nearly five lines with a breadth of more than half a 
line. This singular variation, though not of very common 
occurrence, cannot be looked upon as accidental. 
