A certain amount of uniformity, especially as regards the flatness of the carapace, may be inferred to exist in this family from the number of genera with names all alike ending in -plax, as Acanthoplax, Ilyoplax, Hemiplax, Camptoplax, Bathyplax, with many others.

The genus Geryon, Kröyer, 1837, may claim a passing notice as one of those instances in which systematic arrangement finds itself at fault. It is sometimes placed among the Cyclometopa and sometimes among the Catometopa. Mr. Miers says that it is very nearly allied to Pseudorhombila and Pilumnoplax in the latter, and to Galene in the former group. That, on the theory of the evolution of different groups from a common stem, such inosculant forms are almost sure to occur, has long been recognised. Darwin himself humorously admits that while as a theorist he delighted in coming across them, as a naturalist engaged in classification he found them an unmitigated nuisance.

Family 3.-Grapside.

The carapace is depressed or moderately convex, more or less quadrilateral, with the lateral margins straight or slightly arcuate. The 'front' is never very narrow, in general decidedly broad. The orbits and eye-stalks are of moderate size. The third maxillipeds have the fifth joint articulated at the apex or the front outer angle of the fourth. The chelipeds in the adult male are usually subequal, moderately developed. In the walking legs the seventh joint is stiliform, compressed, and either smooth or spiniferous. The pleon at the base usually covers the whole width of the sternum between the last pair of legs.

The species are almost always littoral or shallow-water forms, with a rare exception in deep water.

In this family there are about twenty-four genera.

Grapsus, Lamarck, 1801, is a wide-ranging genus which was brought to the notice of Europeans a century and a half ago in the species Grapsus maculatus (Catesby, 1743 and 1771), to which Bosc in 1802 applied the better

known name of Grapsus pictus. Professor Th. Barrois, in his account of the Crustacea of the Azores, speaks of this and two companion species as running with astonishing velocity among the rocks near the sea. The brilliantly coloured Grapsus, with its limbs of a marvellous red, he calls a superb species. As it occupies by preference the sides of the perpendicular cliffs, it is easy to believe the statement that prodigies of agility and cunning are required for capturing uninjured specimens. In Charleston Bay Bosc had a much easier task. There he noticed that these crabs almost always kept themselves concealed under stones or pieces of wood, and, as these objects are rare in that locality, every day on the retreat of the tide he was sure to find fresh specimens of Grapsus under the hiding-places from which he had taken other specimens on the previous day. Darwin, in A Naturalist's Voyage,' when speaking of the nests of the tern at St. Paul's Rocks in the Atlantic, says, 'It was amusing to watch how quickly a large and active crab (Grapsus), which inhabits the crevices of the rock, stole the fish from the side of the nest, as soon as we had disturbed the parent birds. Sir W. Symonds, one of the few persons who have landed here, informs me that he saw the crabs dragging even the young birds out of their nests and devouring them.' The voracity and audacity, the cunning and speed and jumping powers of these crabs of St. Paul's Rocks are amusingly described in the 'Log Letters of the Challenger,' by Lord George Campbell, who however, saw no proof that they ate the young birds.

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About a dozen other genera have been formed with names in which Grapsus is part of the compound, as Geograpsus, Paragrapsus, Platygrupsus, and the like. Several of these contain species which were at one time included in the genus Grapsus, and which are by no means very remote from it.

The Cancer marmoratus of Fabricius has been transferred from Grapsus to Pachygrapsus, Randall, by Stimpson, and to Goniograpsus, Dana, by Miers. It is a European species, common among chinks of the rocks in the Adriatic. It prowls about on the shore by night to feed on dead

THE GULF-WEED CRAB

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It is said to be timid,

animals cast up by the waves. running off with great speed if scared, but if stopped it shows temper and nips hard. It is also very common, according to Lucas, in Algeria, where it is eaten by the poor. Fine specimens for a naturalist's collection are not easy to catch because of their extreme readiness on the least alarm to ensconce themselves deep in rifts of the rock. If in their headlong haste they sometimes slip into a hole too shallow to contain them entirely, the pursuer will still be likely only to obtain their cast-off legs, since they readily relinquish them all rather than be captured.

Nautilograpsus, Milne-Edwards, 1837, like some of the genera previously described, has third maxillipeds which do not form a complete operculum. In 1825, in Bowdich's Excursion to Madeira and Porto Santo,' Leach gave to this genus the name Planes, a wanderer, but from want of a sufficient accompanying description this has been regarded as technically only a manuscript name, not entitled to priority. It may, however, be doubted whether this is a right decision, since a figure of the type species, Planes minutus (Linn.), was appended, and there appears to be but a single species in the genus. The name of wanderer is very appropriate, since this, the common Gulf-weed Crab, is said to occur nearly everywhere on floating weed in the temperate and tropical seas of the globe. If, as is probable, it was the presence of this little crab on the Sargassum bacciferum that Columbus adduced as an argument to prove to his despairing sailors the proximity of land, it was not quite so much to the point as the sailors appear to have thought it. Columbus himself had other and more satisfactory reasons for his own confidence. Patrick Browne calls it the Turtle-Crab, remarking, 'I found this insect on the back of a turtle, near the western islands.'

Eriocheir, de Haan, 1835, meaning 'woolly-hand,' contains a species, Eriocheir japonicus, of very singular appearance, the great claws looking as if they were muffled up in cuffs of long fur. It is represented in the accompanying plate, which is reduced from de Haan's work.