A HISTORY OF CORNWALL besides being unattended by any attempt to disprove Norman's now fully accepted view that this species and the preceding one should alike be called Maera othonts (Milne-Edwards). For Megamoera brevicaudata. Bate, ' dredged in Plymouth Sound,' l the proper title is now held to be Elasmopus rapax (A. Costa). 2 Pherusa fucico/a, Leach, is mentioned by Bate as known to him through specimens from Falmouth and Polperro. It is not quite certain what species these specimens may have repre- sented, but it is tolerably clear that the species which Bate and Westwood describe as Gammardla brevicaudata and G. normanni are the male and female of the species which they figure as Pherusa fucico/a, Leach, 3 so that they have assigned three different designations to a single species. Leach's being the earliest of the three is the one that remains valid. In Cornwall, as elsewhere, the fresh- water Gammarus pulex (Linn.) is abundant, and so is its marine congener G. locusta (Linn.), together with the more littoral G. marinus, Leach. 4 Bate adds G. campy/ops (Leach), of which he says, ' It is not very common, but it has been taken among other places in Plymouth Sound.' 8 Leach originally named it G. camylops, and justified its ill-formed name, meaning bent-eyed, by description of the ' eyes shaped like the capital letter S, extending from the upper part of the superior to the upper part of the base of the inferior antennae.' 6 The Talitridae, which more than any other amphipods show a tendency to terrestrial life, are often on that account put foremost in classification. From the point of view of evolution, they will more naturally follow the Gammaridae, which may be regarded as the central family. This view, at least, is based on the supposition that all the other families can more easily be conceived as diverging from the Gammaridae, than the Gammaridae from any one of the others. The Cornish species of Talitridae are Ta/itrus saltator (Montagu), the sand-hopper ; Orchestia gammarellus (Pallas), the shore- hopper ; Talorchestia deshayesii (Audouin), also a sand-hopper ; Hyale prevostii (Milne-Edwards), recorded by Bate as AHorchestes Nillsonii (Rathke),' for which A. nilssonn should be read, and Hyale pontica (Rathke), of which Bate, using for it his own name Nicea Lubbockiana, says, ' I have received specimens of this species from Falmouth and Penzance." 7 Cocks mentions only the first two species given above in this family. The Aoridae offer the widely distributed Aora gracilis (Bate), obtained by that author ' from St. Ives and off the Eddystone,' 8 a species perhaps not properly distinguishable from A. typica, Kroyer, but in any case remarkable for the elongate first gnathopods of the male. In these organs it is not the sixth joint that is modified to assist in the act of prehension, but the fourth is abnormally produced for that purpose. Microdeutopus versiculatus, Bate, has been dredged by him in Plymouth Sound. It was transferred by Norman in 1905 to a new genus Coremapus. Of his Lembos websterii, Bate says, ' Mr. Webster dredged this species in Falmouth Harbour." 9 Both these genera agree with Aora in having the first gnathopods larger than the second ; but in the male of Coremapus it is the fifth joint, not the fourth, that is produced to help prehension, and in Lembos neither fourth nor fifth, the gnathopods being subchelate in the ordinary fashion between the finger and the sixth joint. In the family Photidae the red-eyed species called by Bate Eurystheus erythrophthalmus (Liljeborg), and said to be ' not uncommon in Plymouth Sound,' 10 should take its specific name from the earlier Gammaru maculatus, Johnston. 11 Isaea montagui,M.i e-'Edwards, is mentioned by Bate in his ' Revision ' of Couch rather confusingly, since he assigns no Cornish locality. In his earlier work he wrote, ' We have procured it from some refuse brought by the trawlers from the neighbourhood of the Eddystone. All our specimens were taken from the back and branchial chambers of Maia squinado ; they seemed, indeed, to exist among the thick stiff fur on the carapace of this spider-crab as if they were in their accustomed habitat, their prehensile legs being peculiarly adapted for holding themselves on that animal.' 12 In the ' Revision ' 13 this is transferred almost verbatim to the account of the so-called Acanthonotus tnvenii, which has no limbs specially prehensile, instead of having an extra supply, as is the case with Isaea montagui. The Ampithoidae furnish Ampithoe rubricata (Montagu), found by Cocks ' under stones, algae, etc., Gwyllyn-vase, Swanpool, Bar-point ; not uncommon.' A. littorina, Bate, is doubtless a synonym of this species. Sunamphitoe conformata, Bate, was taken by him in Plymouth Sound. The later S. hamulus, Bate, which is perhaps identical with the preceding, was sent to him from Penzance. 14 Pleonexes gammaroides, Bate, is not included in his 'Revision,' but under the heading Amphithoe gammaroides he earlier, wrote of specimens which ' were sent to us by the late Mr. Barlee, who obtained them at Penzance.' 15 In the first and the last of these three genera the mandibles have ' P a lp s >' but in Sunamphitoe these are wanting. In Pleonexes the hinder peraeopods have the sixth 1 ' Revision,' p. 55. * Walker, in Ann. Nat. Hist. (1895), Ser. 6, vol. xvi, 671. 3 Brit. Sess. Crust, vol. i, 255, 330-333. 4 Cocks, in his often quoted work, p. 83. 6 ' Revision,' p. 54. 6 Edin. Encycl. (1813), vol. vii, 403. 7 'Revision,' p. 44. 8 Ibid. p. 52. 9 Ibid. p. 52. ' Ibid. p. 54. " Brit. Sess. Crust, vol. i, pp. 354, 399. Ibid. vol. i, p. 216. 13 Op. cit. pp. 47, 48. 14 Ibid. pp. 56, 57. 15 Brit. Sess. Crust, vol. i, p. 428. 280
