Page:VCH Cornwall 1.djvu/328

A HISTORY OF CORNWALL maxillipeds. In the family Aegidae, Cornwall has two species known. The characters of Rocinela danmoniensis, established by Leach in 1818, were first rescued from obscurity by Bate and Westwood, but since Cocks in 1850 records it from 'Trawl and dredger's refuse,' Bate is not quite accurate in saying, ' This for half a century was known only by one specimen in the British Museum, named by Dr. Leach.' * He and his colleague say, ' We have received it from Polperro, where it was taken by Mr. Loughrin.' 2 I myself am indebted to Mr. Rupert Vallentin for a specimen taken off a mackerel at Falmouth. The species which Bate and Westwood call Aega bicarinata, Leach, labours under some obscurity. They give for it a North of England locality, resting on a specimen now known to be Aega strSmii, Liitken. This has been thought to throw some doubt on the name which they apply to their Plymouth specimen. 3 In any case Aega rosacea (Risso) takes precedence of Ae. bicarinata* The emarginate telson separates both this and At. strSmii from R. danmoniensis in which the telson is rounded. Also in Rocinela the maxillipeds are four-jointed, but six or seven jointed in Aega. The family Sphaeromidae has several Cornish genera. Cocks names Sphaeroma serratum, Fabricius, from ' Under stones, &c., Gwyllyn-vase, &c.' Bate adds S. rugicauda, Leach, which he transmutes into rugicandata, saying, ' In Cornwall we have found it at the mouth of the River Tamar. 6 Naesa bidentata (Adams) was found by Cocks ' Under stones, in crevices of rock &c., Gwllyn-vase : not uncommon.' Bate and Westwood note it as ' common amongst weed between tides on the rocky shores ' of Cornwall, and as found at Polperro by Mr. J. Couch. They say, ' It is generally associated with Dynamene Montagui, of which we think it may possibly turn out to be the male.' 6 Leach's three species D. montagui, D. rubra, and D. viridis are pretty constant companions of N. bidentata, and are probably not fully adult forms of that species, now called Dynamene bidentata (Adams). Cocks records rubra and viridis, which are mere colour varieties, under the genus Cymodocea, more properly called Cymodoce. He found Leach's two species C. truncata and C. emarginata ' in crevices of rocks, &c., Gwyllyn-vase.' Of the latter Bate and Westwood say ' Mr. John Cranch found specimens, less strongly granulose, at Falmouth.' 7 Should the two named species be united C. truncata has priority. Campecopea hirsuta (Montagu) is reported by Cocks from ' Trawl refuse, extreme low- water mark, Gwyllyn-vase : very rare,' but by Bate as taken in some profusion ' at Polperro, among the small dry fuel that exist on the surface of the rocks within reach of the spray of the sea, but where the sun appears to drain off all moisture.' Bate adds C. cranchii, Leach, as ' Found with the preceding, and is probably the female. Taken at Falmouth as well as plentifully mingled with the former species in the localities named.' 8 There can be no doubt that C. cranchii is the female of C. hirsuta. The fucus described by Bate is the Lichina pygmaea, of which these little crustaceans might easily be thought to be constituents. The family Limnoriidae presents the wood-boring Gribble, Limnoria lignorum (J. Rathke). Under the later name L. terebrans, Leach, Cocks reports it from ' Gwyllyn-vase, Penzance, etc. : not common.' Bate has knowledge of it ' all round our coast, in submarine timber, which it eats with avidity. 9 The tribe of the Valvifera includes two families, the Astacillidae and Idoteidae. In both of these the pair of ventrally placed valves that open and shut upon the pleopods are in reality the uropods or terminal appendages, though their position dissembles the fact, and has a great tendency to mystify the observer. Astacilla longicornis (Sowerby), formerly placed in the genus Arcturus, is recorded by Cocks from ' Trawl refuse : not uncommon.' The great length of the fourth peraeon- segment is a striking feature in this genus. The marsupium of the female consists of two plates, whereas in Arcturus it is composed of four. Idotea balthica (Pallas), /. pelagica, Leach, /. emarginata, Fabricius, and /. linearis (Linn.), are all attested as Cornish by Bate, 10 and the last two also by Cocks. The first and commonest of the four has had many designations, of which /. tricuspidata has had the greatest vogue. /. neglecta, Sars, has recently been recorded by Norman from Falmouth. As to the round-ended Zenobiana prismatica (Risso), Bate and' Westwood, who call it Idotea parallela, say, ' We have obtained this species from Falmouth, taken by Mr. Barlee, and from Polperro whence it was sent to us by Mr. Loughrin.' n Stenosoma acuminatum, Leach, is recorded by Cocks as an Idotea, from 'Castle point, Gwyllyn-vase, East: not uncommon.' Concerning Idotea appendiculata (Risso), which perhaps also belongs to Stenosoma, Bate and Westwood say, ' We have received it from Mr. Loughrin from Polperro.' 12 The tribe Asellota and the family Asellidae are alike named from the freshwater genus Asellus of Geoffroy, which has the peculiarity that neither the first nor the last of the pleon 1 'Revision,' p 65. * Brit. Sess. Crust, vol. ii, p. 293. * Ibid. p. 280. 4 SchiOdte and Meinert, Naturhist. Tldsskrift (1879), Ser. 3, vol. xlii, p. 353. ' 'Revision,' p. 69. * Brit. Sess. Crust, vol. ii, p. 432. 7 Ibid. p. 429. " 'Revision,' p. 70. 9 Ibid. p. 67. ' Ibid. p. 68. 11 Brit. Sess. Crust, vol. ii, 392. " Brit. Sess. Crust, vol. ii, 397. 276