Dr. H. A. Nicholson on the Genus Climacograpsus. 383 
first described by myself from British specimens which I ob- 
tained from the Skiddaw Slates, our British equivalent of the 
Quebec group of Canada. I subjoin figures of the species ; 
but it will be unnecessary to give any detailed description, 
more especially as all extant British examples are in a state of 
preservation which does not admit of the ij. ek of mi- 
nute points of structure. 
4. Climacograpsus antennarius, after Hall, showing the cell- Ke 
from the Quebec group. 6. Small specimen of the same, from the 
Skiddaw Slates; nat. size. c. Base of another specimen from the 
Skiddaw Slates, with unusually long basal spines; enlarged. 
The essential characteristic by which C. antennarius is di- 
stinguished from its relatives C. teretiusculus and C. bicornis 
this does not appear to be exceeded. The cellules, according 
to Hall, are from twenty-four to twenty-eight in the space of 
