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 Portunidas 

 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- 

 placidas, 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,' 2 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 Pinnotheridas, Byerley records Pinnotheres pisum (Linn.) as ' very 

 common in Muscles and Modioli,' and adds that ' the females from the latter 

 are often very large.' s 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 veferum (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.' 6 



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. 2 Fauna of Liverpool, p. 5 1 . 8 Ibid. 



* Trans. Liverpool Bio/. Sac. vi. 98. 8 Fauna of Liverpool, p. 52. 



