A EARE SPECIES 145 



out by Milne-Edwards a few years afterwards. Dr. Hen- 

 derson was only able to identify the Challenger specimen 

 with de Freminville's 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 Raninida?, 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 cassivelaumis, but this 

 notion is based only on a very slight superficial resem- 

 blance between the two species. 



Since Lyreidus 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.' 



