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. 



* 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. 

 X 249 32 



