CRUSTACEANS 



The county of Cornwall has for its size far more coast-line than any other English county, and 

 that coast-line is strongly indented. It juts into the ocean further to the west and further to the 

 south than any other part of Great Britain. It has a northern as well as a southern aspect. 

 Harbours great and small receive vessels of every description arriving from far and near. Its interior 

 is diversified. The margin between tide-marks is very far from uniform in character. The sea 

 outside is variable in depth, and contains numerous islands which are reckoned as part of the county. 

 From all these circumstances combined those who understand the habits of crustaceans would expect 

 Cornwall in this branch of its fauna to compare favourably with any other equal area in the kingdom. 

 That it does in fact respond to this presumption has been proved by the marine researches of several 

 enthusiastic observers. Jonathan Couch, the famous surgeon of Polperro, set a distinguished 

 example, which was excellently followed by his son Richard Quiller Couch of Penzance, by his 

 disciple and helper William Laughrin, A.L.S., the Polperro coastguardsman, by W. P. Cocks, Esq., 

 assiduous in recording the fauna of Falmouth, and quite recently by my friend Mr. Rupert Val- 

 lentin, F.L.S., who has found time for home work as well as exploring the far-off waters of the 

 Falkland Islands. To the results obtained by residents, important additions have been made by 

 visitors, such as Canon Norman, F.R.S., Dr. G. S. Brady, F.R.S., and David Robertson, D.C.L., 



* the naturalist of Cumbrae.' One who was neither exactly a resident nor exactly a visitor must 

 also certainly be mentioned. Spence Bate was a dental surgeon long in practice in Plymouth, whence 

 he was able to make natural history excursions as readily in this his native county as in the one of 

 his adoption, and in discussing the Crustacea of Plymouth Sound he recognizes that at least in those 

 waters there is a faunistic partnership between Cornwall and Devon. In response to an invitation 

 from the Royal Institution of Cornwall he published in 1878 ' The Crustacea of Couch's Cornish 

 Fauna, revised and added to by C. Spence Bate, F.R.S.' 1 Considering the high reputation he had 

 won by his numerous writings and his really extensive knowledge in this department of study, the 

 task involved in this revision must have seemed to all concerned both appropriately placed and easy 

 of performance. It fell, however, upon a time when no doubt Mr. Bate was extremely pressed by 

 other engagements. The twenty-five years, however, which have elapsed since Bate's essay 

 appeared, have been fruitful in exact studies of the crustacean class carried out by men of distinc- 

 tion. It is far less excusable, therefore, now than then to be in the wrong ; but on the other hand 

 it is far less easy to explain, or even indicate briefly and concisely, all that is known of an enlarged 

 and expanded science. 



A paradox meets the beginner in the fact that multitudes of Crustacea are not crustaceous. 

 The external chitinous skeleton so essential for providing the muscles with points of attachment may 

 be hardened by deposits of lime to the consistence of stone earthenware, or from the brittleness of 

 delicate china it may pass through conditions of membranous and papyraceous flexibility. The 

 mode of life, too, has acted vigorously upon the outward form and general appearance. Aquatic 

 species as compared with terrestrial, marine with freshwater, the parasitic and the independent, such 

 as swim or walk in contrast with others that are fixed to a rock or any object from which they 

 cannot detach themselves, may well be expected to differ. But the amount of difference often goes 

 a good way beyond expectation. Sometimes, to be sure, it falls a little short of it. But at all events 

 no one without instruction, without using knowledge laboriously and gradually accumulated in the 

 past, could tell that the Malacostraca, Entomostraca, and Thyrostraca that is to say, crabs and 

 shrimps and wood-lice, water-fleas and fish-lice and barnacles all alike rightfully belong to the 

 crustacean class of the animal kingdom. 



The first of these three divisions is also popularly the best known. Of the English species 

 belonging to it a large number have been observed in this county. All the principal sub-divisions 

 will have to be included in our survey, the Decapoda (brachyurous and macrurous), Schizopoda, 

 Stomatopoda, Sympoda, Isopoda, and Amphipoda, all named from the number, structure, or position 

 of the trunk-legs. These sub-divisions embrace the crabs, hermits, lobsters, crayfish, prawns, shrimps, 

 wood-lice, scuds, and sandhoppers, with various other kinds of which common parlance has hitherto 



1 Journ. Roy. Inst. of Corntv. part ii, No. xix, pp. 174. It will be convenient to quote this work as 



* Revision.' 



255 



