A RARE SPECIES 145 
out by Milne-Edwards a few years afterwards. Dr. Hen- 
derson was only able to identify the Challenger specimen 
with de Freminvilles by help of a pencil-drawing pointed 
out to him by Professor Alphonse Milne-Edwards in the 
library of the Natural History Museum at Paris. The 
elder Milne-Edwards, though assigning the species to the 
vicinity of the Raninidee, did not alter the generic name. 
Judging by the rudimentary nature of the eyes and the 
structure of the limbs, Dr. Henderson conjectures that 
this crustacean may be fossorial in habit. If it be so, the 
rarity of its capture would be the less to be wondered at. 
To one of the genera of this family may probably be 
assigned the West-Indian crab, which for some inscru- 
table reason has been called the Mamma Shrimp. It is 
figured and described by Patrick Browne in his ‘ History 
of Jamaica.’ Herbst (Bd. I., p. 196), in 1790, supposed 
it to be a near relation of Corystes casswvelaunus, but this 
notion is based only on a very slight superficial resem- 
blance between the two species. 
Since Ivyreidus and Zanclifer agree in having the 
orbits ill-defined, the statement that in this legion ‘the 
orbits are well marked’ is too absolute. In the defini- 
tions of natural history, where living things are con- 
cerned, almost every assertion sooner or later requires to 
be qualified by the adverb ‘ usually.’ 
12 
