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 CRUSTACEANS ' Mr. Montagu considers this as the male of P. emarginatus. Mr. Leach thinks that emarginatus may prove to be an accidental variety of this species, but considers the distinctions as too strong for usual sexual dis- tinction.' ' Since the Mr. Leach referred to was the writer himself who had instituted both species, and since by his own confession the strong distinctions between them concerned only a single particular, the char- acter and constancy of that solitary difference become important. Leach himself suspected that the emargination in his female specimen might be an accidental variety, and as it does not appear to have been again observed the name founded upon it has been set aside by general consent in favour of the more appropriate and contemporary name arcuatus. The same species was named rondeletii by Risso in 1816, and Bell with justice criticizes Milne-Edwards ^ because he has ' kept Risso's name against the law of priority of description." By inadvertence later in his work however he himself uses the repudiated name, where, speaking of a particular season, he says : ' At Bognor I found multitudes of Portums rondeletii, which absolutely swarmed in the prawn and lobster pots, but not a specimen of any other species was obtained there.' * Of P. marmoreus. Leach, Bell says: 'At Hastings I procured a single specimen which I found in a shop where shells, Crustacea and other marine productions were sold, but it was certainly native at that place.' ^ The Natural History of Hastings records it as not uncommon. On the other hand that catalogue enters the P. holsatus of Fabricius with a query, which ' indicates that there is some doubt whether the specimen referred to was really of the species named.' * Leach instituted a species P. lividus. Bell, following Milne-Edwards, identifies this with the earlier holsatus, but he is further persuaded that P. marmoreus. Leach, is only a variety of the same. Still he has not quite the courage of his conviction, for he describes marmoreus and holsatus as if they were two distinct species. Of the ' marbled swimming crab ' he says : ' The colours of this species are exceedingly varied and beautiful, particularly in the males. Buff, light-brown, deeper brown and brownish-red are arranged over the carapace in varied but always exactly symmetrical patterns. The only way in which these beautiful markings can be preserved is by raising the carapace, taking out the soft parts and drying the specimens in a shady place in a brisk current of air. If they are put into spirit the whole of the beauty of the colour is lost." Elsewhere he suggests that faded specimens of P. marmoreus might easily be mistaken for P. holsatus!' Apart from distinction of colour the points chiefly relied on for separating the latter species from the former are that the middle tooth of the front is slightly more prominent, and that the last joint of the hindmost leg has the apical point projecting from an otherwise more broadly rounded terminal ' Edinburgh Encyclopadia (1813), vii. 390. 2 Histoire Nalurelle des Crustach (1834) '• 444- * British Stalk-eyed Crustacea, p. 98. X 249 32
 * Loc. cit. p. 107. 6 Loc. cit. p. 107.
 * Loc. cit. p. 41 compared with p. 5. ' Loc. cit. p. 106. * Loc. cit. p. ill.