Dr. H. A. Nicholson on the Genus Climacograpsus. 379 
e 
meant for. I am also perfectly satisfied that it is wholly im- 
for teretiusculus, unless it can be demonstrated that the original 
G. scalarís was a bicellular form. The promoters of this 
substitution appear to have proceeded upon the entirely erro- 
neous belief that unicellular Graptolites do not exhibit * sca- 
lariform " views. On the contrary, numerous instances occur 
in which monoprionidian ds si exhibit * scalariform " 
proved by the occurrence of numerous scalariform VY EE. 
im rocks (such as the Coniston Grits of the north of England) 
in which the most careful search has hitherto failed to reveal 
a single double-celled Graptolite. I ux gen a cut (fig. 4) 
showing the phenomena above mentioned, as they occur in 
G. colonus, Barr., and G. priodon, Bronn—all the specimens 
figured having been obtained from deposits which have hitherto 
yielded no examples of either Diplograpsus or Climacograpsus. 
. If, then, the original G. scalaris, Linn., be a Graptolite, it 
1$, to say the least of it, quite as likely to be the scalariform 
impression of a monoprionidian species as of a double-celled 
rm. I am, therefore, decidedly of the opinion that there are 
no grounds for accepting the change promi by Hall and 
followed by Carruthers—a change which would substitute for 
