Page:VCH Cornwall 1.djvu/314

 A HISTORY OF CORNWALL involved in the species which Couch describes as Gelasimus Be/Hi, 1 which Bell in whose honour it was named, thinks may probably 'prove to be the female or young male of Gomplax rhombotdes and which Bate prudently does not attempt to identify, leaving it as 'a very doubtful spec.es to the conjecture of future observers. 3 Unfortunately the figure of which Couch speaks was seemingly never published, and his description tantalizingly leads to no decision. The species, he says, is ' frequently found in the stomachs of fishes taken in depths varying from five to more than twenty fathoms ' Though the carapace is in general like that of Goneplax and has two well-marked teeth or hooks on the lateral margin, the inter-orbital front is more advanced, so that when the eye-stalks are withdrawn into their orbital cavities, their extremities point a little backward. Both claws are of equal size, and less than the transverse breadth of the carapace.' Couch expressly adds : I find but little difference in the form of the male and female, and none in the proportions of the claws, though such is the case for the most part in crustaceans.' If he had at command adult specimens, this last remark would decisively dismiss Gmepla*, in which the chehpeds of male and female d.ffer greatly in size, and it would be no less opposed to Gelasimus (now called Uca in which the male alone has one cheliped monstrous in size compared with the other. Couch s reference to Plate XV 111, Fig. 10, in Milne-Edwards's Histoire naturelle des Crustach, which represents Gllaamu annuhpes, do. not of itself throw any light upon the matter. In the family Grapsidae, Cornwall may not unfairly be credited with the little squarish, broad- fronted, ' Floating crab,' so well known in the Sargasso Sea and otherwise widely distributed. I have myself received it from the gulf-weed, from South African waters, and from the Falkland Islands. It varies much in colouring. It has been sometimes called Planet Llnneana, and sometimes Nauttlo- grapsus minutus, but the more correct name is Plane; minutus (Linn.) Couch sent to Bell a very voune specimen from the Cornish coast, which is extremely small, being not more than a l.ne in breadth ' 4 Bell adds : ' It is quite perfect, although so small, and is of a very pale grey colour, with small dark dots.' Cocks found it at 'Bar, Castle-point, after a storm, October, 1845, and one mutilated specimen, 1848, from the stomach of a fish.' At a later date Couch reports two full- grown examples adhering closely under the tail of a Hawk's-bill turtle taken in the Channel not far from the French coast and brought alive into Polperro.' R. Q. Couch, m the Report of the Penance Natural History Society for i8 4 8, 6 writes : ' Among the crustaceans we have one new species to be added : this is not only a novelty to the county, but to the kingdom. It n a species of Graftus, and was taken below the baths in Mount's Bay. The recognized species on our coast is G. L,nneana, and that is so rare that but little is known of its history or habits. Several species inhabit the Sargasso or gulf-weed, but the Cornish species was found amid the roots of the Laminana ****, the common sea-weed of our shores.' The new Grapsus was perhaps only the accustomed Planes which, having strayed away from the Sargassum bacciferum, had taken refuge in the sea-weed, and from some difference in colouring was supposed to be a novelty. The family Pinnotheridae supplies the minute 'Pea-crabs,' Pinnotheres ptsum (Linn.) and P wterum, Bosc. Of the former Couch says: 'This species seems rare with us and only found in the Mussel shell, the natural inhabitant of which it either finds diseased, or renders so 1 have never found it in the Pinna, as reported by authors, though many have been examined for that purpose.' 7 Cocks says that it is 'found between the folds of the mantle of the Myt.lus edulis, M incurvatus, cardium echinatum, etc. : not uncommon.' Of P. veterum, which Bell calls the ' Pinna Pea crab,' Couch, who calls it the ' Ancient Pea crab,' says ' this is more rare than the last named' Cocks says that it is 'found between the folds of Pinna ingens, Modiola yulgaris, etc from deep water : not uncommon.' In the first species the male has an arched front, in the second the front is emarginate. In the female of the first the pleon is broader than long, ,n the second it is loneer than broad. 8 It would be interesting to know whether Couch s opinion as to the con ditions of companionship between a Pinnotheres and a Mussel were based on his own observations or not. The Oxyrrhyncha of late years have excited wide-spread interest by the correlation between various points in their structure and their practice of wearing clothes. They have hairs, spines, and tubercles well adapted for retaining the marine flora and fauna or the mud and sand with wh. they are so frequently overlaid. It is now known that in carrying this disfiguring burden the shell of the crab ought not to be compared to the field of the slothful. It is a cultivated field. The nippers of the crab have their articulations nicely calculated for reaching the different parts of the body to which disguising materials are to be attached. When circumstances render a particular raiment inappropriate, it is taken off and a more suitable covering assumed in its place When the artificial dress is lost by the periodical shedding of the natural coat, the fresh surface i 1 Fauna p 73 ' Brit - Stalk-eyed Crustacea, pp. 130, 132. Revision,' p. 19. ' Brit. Stalk-eyed Crustacea, p. 137. . 5 Brit. Aistc. Rep. for 1867, and Revision,' p. 21 Op. at. p. 178. 1 Fauna, p. 72. * Brit. Stalk-eyed Crustacea, pp. 121, 126. 262