CRUSTACEANS the other. The great eatable crab has a carapace much broader than long, with its anterior margin cut into nine lobes on either side external to the orbits, while the masked crab has the carapace notably longer than broad, with some lateral denticles, and on its back in low relief of natural sculpture the lineaments of a human face. On the other hand the three Portunidae show no great differences in the length and breadth of the carapace. They are called swimming crabs because of their agility in natation, which is promoted by the flattened blade-like termination of their fifth pair of legs. The shore crab, however, which is a rapid walker and tolerant of the open air, is distinguished from the other two by having its fifth pair of toes very moderately expanded. They all have the anterior margin on each side cut into five teeth outside the orbits, but while in the cleanser crab these teeth are prominent, in the nearly orbicular carapace of ' Henslow's swimming crab ' they are flattened, so as only slightly to interrupt the circle. Distinctive characters may be drawn also from the dentation of the ' front,' that part of the anterior margin which lies between the orbits. In the Catometopa the front is more or less bent downward. Within this tribe is the family Gone- placids, with the species Goneplax angulata (Fabricius), the angular crab, which Mr. A. O. Walker records with what looks like an air of doubt and suspicion, ' One specimen said to have occurred at Southport (C. H. Brown). A Mediterranean species.' ^ It occurs in fact much nearer home than the Mediterranean, being not uncommon in the waters of South Devon, but there is reason to think that it is scarce in northern seas. Byerley speaks of ' specimens taken rarely in shrimp-nets,' ^ without specifying any locality. Its quadrate carapace, its long-stalked eyes, and special colouring would not allow it to be easily mistaken. In the male the chelipeds are also of striking elongation. Any doubt as to its occurrence at Southport is probably based not on any question of identification, but on the possibility that the specimen seen may have been imported by fishermen from a distant cruise. In the family PinnotheridEe, Byerley records Pinnotheres pisum (Linn.) as ' very common in Muscles and Modioli,' and adds that ' the females from the latter are often very large.' ' Whether Byerley selected the correct specific name it is impossible to say. His remark on the size of the females would rather point to Pinnotheres veterum (Bosc). But as the waters of Lancashire abound in the molluscs whose shells are frequented by these little soft-coated crabs, there is little doubt that both species are to be found in the district. The Macrura anomala are not particularly demonstrative in this region, although the hermit, Eupagurus bernhardus (Linn.), is 'abundant every- where,' * and the so-called porcelain crabs, which are not true crabs, are evidently also plentiful. Byerley and Walker both represent the broad-clawed Porcellana platycheles (Pennant) as less common than its narrow-armed con- gener, P. longicornis (Linn.), Byerley supplying the information, presumably founded on experiment, that the former species ' seems to live for a long time in captivity, even with a small quantity of sea-water.' ^ The genuine Macrura, or long-tailed Decapoda, including crawfishes, crayfishes, lobsters, prawns, and shrimps, make a fairer show than the two preceding groups. It is allowable perhaps to assign to the fauna of Lancashire 1 Loc. cit. p. 96. ^ Fauna of Liverpool, p. S i . ' Ibid.
- Trans. Liverpool Biol. Soc. vi. 98. ^ Fauna of Liverpool, p. 52.
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