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 CRUSTACEANS The Romans were a highly practical people, and the poet of widest renown among them has left us the aphorism that it is im- possible for every one to do everything. It appears to be equally true that all counties cannot embrace all branches of natural history with a complete efficiency. A region may have striking features of scenery appealing not only to aesthetic tastes but to the curiosity of those who would fain understand the slow moulding of the land they live in and unravel the far-off story of what happened before its history began. In such a region there may be a great variety of attractive objects, fossils and minerals, exquisite fluor spar, marbles of great beauty and value ; there may be mysterious caverns with wonderful stalactites and bones of extinct yet half familiar animals ; there may be dripping wells in which treasures the most trifling or the most precious a tuft of moss, the egg of a robin, or a skull which the owner has ceased to require may be rendered almost imperishable by a calculated thickness of in- crustation. Since all these and several other engaging attributes belong to Derbyshire, there is no great reason for surprise that the subject of this chapter has hitherto been passed over with an almost absolute neglect. It is time that its turn should come, and an endeavour will here be made to show that carcinology, the science and study of crustaceans, has a fair and promising field in this county. It will be tolerably obvious to every reader that in regard to this pursuit there are facilities enjoyed by the maritime outskirts which are entirely denied to the central districts of England. At any con- siderable distance from the coast the majority of the inhabitants may pass their whole lives without ever suspecting that any crustaceans what- ever are fellow-tenants with themselves. They are impressed by the fact that crabs and lobsters, prawns and shrimps have to be imported from the sea and are never found indigenous to the midlands. It is not, or till recently was not, any part of popular education to explain that in close affinity with the commercial species just mentioned there are others, not large, not eaten, not highly prized, which live on land and on terms of an indifferent intimacy with mankind. Also among things not generally known may be included the fact that, in addition to a score or so of terrestrial species, we have about two hundred that occupy the fresh waters of this country. Omitting the cirripedes or barnacles which are not tempted to forsake our shores, we may divide the rest of the crustacean class into Malacostraca and Entomostraca. It is the latter division that supplies a 102