26 Notes on the Irish Crustacea. 
rivulosa, and X. tuberculata. Of the first (Montacu’s crab), the 
species not uncommon being frequently taken under stones, 
between tide-marks, on the southern and western coasts. It is 
the larger species of the three, and subject to variation of colour 
of the carapace and claws. In the marine fauna of the coast of 
Clare, Dr. Kinahan mentions its occurring under stones about half 
way down the littoral zone. Of Xantho rwulosa, he says but 
very little appears to have been known of either its distribution 
or habits. William Thompson only gives the authority of 
Colonel Portlock, who obtained one specimen in July, 1839, in 
the county of Antrim. Understanding its extreme rarity, others 
in the locality were sought for, but in vain. Kinahan observes 
that it may be considered as frequenting the southern, western, 
and north-eastern coasts, but in such instances, I would be 
doubtful of its identity, and of its separation from X. florida as 
a sub-littoral species. 
In Professor Kinahan’s paper, read before the Natural History 
Society of Dublin, 12th December, 1876, on Xantho rivulosa 
(Risso’s crab) and other decapodous crustacea, occurring at Valentia 
Island, county of Kerry, hementions it “as one of thetypesof agenus 
which, essentially sub-tropical, reaches its northern limit on the 
British shores—itself an undoubted member of that fauna whose 
scattered members attest the probability of the union of the 
fauna of the west of Ireland and the Mediterranean districts.” Not- 
withstanding he assiduously sought for it, but one specimen 
rewarded his labours. It is not surprising that it has been so 
seldom met, as it is more a deep-water species, taken in the dredge 
in twenty-five fathoms, with broken shells and coral, off the 
Blasket Islands, coast of Kerry. The specimens that I obtained 
were very beautiful in the recent state, and numerous young 
were detected in the hollows of Hschasa foliacea. The several 
species that I examined were perfectly distinct from florida, 
though having some characteristics common to both. Colour of 
pincers and ciliation cannot be considered as distinguishing 
points. There are variations of descriptions, remarkably so in 
the paguride, that no dependence can be placed on excess of 
spinous processes, ciliation, or denticulations, as definite determi- 
nations—hence, in some of the specimens, though partaking much 
of the described characters of rivulosa, approach nearer to 
