A HISTORY OF CORNWALL the neighbourhood of Falmouth ' at every point ; common,' adds that there is a variety ' in some localities very common.' Of this, however, he gives no distinguishing characters. But the Report of the Penzance Natural History and Antiquarian Society for 1852, no doubt drawn up by R. Q. Couch, says, ' Of the common harbour crab (C. maenas) a variety has been brought to the notice of the society, its chief difference being in the waving of the front, there being four instead of three denticulations, and the eyes are wider apart.' 1 Since the young of the species were in those days sometimes mistaken for Planes minutus, briefly described varieties must be regarded with some suspicion. Though Cardnus is a genus of swimming crabs and has the last legs to some extent widened and compressed, the terminal joint in those legs is narrow, so that the genus may be regarded as in some measure linking the Portunidae to the next family, the Cancridae. Cancer pagurus, Linn., the great eatable crab, is as shy as the shore crab is bold. Couch, who adopts for it Milne-Edwards's genus P/atycarcinus, says that the male is called the Stool crab and the female the Bon crab, but offers no explanation of these local names. ' The Bon crab begins to breed when about three inches across the carapace ; and the spawn, after remaining long attached to the parent, is buried beneath some shelter, at all seasons of the year ; but as when engaged in this duty the female feeds but little and commonly hides herself, few of them are taken in the pots. Fishermen mention such instances as somewhat remarkable, though most other crustaceans are familiarly tak^i with the pea (cluster of eggs) attached.' 2 In subsequent years Couch published papers on the process of exuviation, especially as exhibited in this species. His son, after discussing the metamorphosis of Cardnus maenas and Portunus plicatus, says : ' The next species which may be mentioned is the common edible crab, Platycarcinus pagurus. This was treated as the others, but as they generally retire to deep water, and are inactive while laden with ova, the supply of specimens was not so great. After several ineffectual attempts I at last succeeded in hatching them. The body is smaller in pro- portion to the other parts than in the two species previously mentioned. The dorsal shield is shallow, small, and short, being about one-third as long as the tail ; the dorsal spine is long, slender, and bent posteriorly. The eyes are large, sessile, and marked at the circumference of the pupil with radiating lines. The tail is long, stout, and extended, its termination forked.' 3 Omitting the rest of his description of the Zoea, we may remark that apparently he failed to rear the second or Megalopa stage, in which the eyes become pedunculate. Success with the edible crab in this particular has not been recorded by other experimentalists. 4 J. Couch described what he supposed to be a new species as Cancer incisocrenatus. The specimen ' was scarcely a fourth of an inch across the carapace, the form and colour resembling those of the common edible crab, but the area was covered with small warty protuberances. On the margin between the ocular cavities were five segments [teeth or lobes], the central most projecting ; on the lateral margin nine crenations, each, as also those between the eyes, distinctly but finely notched. Antennae small, fine, simple, and with the palpi resembling those of the common crab. Hand claws and walking legs short, the two outer segments of the former with a serrated crest ; the finger also notched at its root. Walking legs with short bristles.' 6 Bate misquotes the name as Cancer insocrenatus, which is unmeaning, and, in place of Couch's statement that the area (of the carapace) was covered with warty protuberances, says that ' the antennae were covered with small wavy protuberances.' His comment is : ' Most probably this is the young of some known species. I am not aware that it has been seen by anyone but Mr. Couch. Bell does not notice it. It appears to me to resemble Pilumnoides of Edwards and Lucas.' 6 Bell, however, does notice it, entering it in the synonymy of Cancer pagurus as a juvenile specimen. 7 The number of lateral crenations condemns any identification with Pilumnoides, but, while not in- consistent with Bell's opinion, it agrees equally with a different interpretation for which, as will be presently seen, there is far more to be said. In the department of teratology the eatable crabs and lobsters not unfrequently supply curious examples, as shown in the writings of Dr. Walter Faxon 8 and Mr. L. A. Borradaile, F.L.S. 9 At a meeting of the Penzance Society ' The Honorary Secre- tary (Mr. G. F. Tregelles) showed a natural curiosity which Mr. J. T. Fleming had kindly lent to the Society. It was the claw of an ordinary crab (Cancer pagurus), from one side of which there grew, at right angles, another small but perfectly formed claw, apparently quite fit for use. He remarked that instances of such redundancy were common in the vegetable world, and exhibited a number of specimens illustrating the phenomenon.' 10 From Plymouth Sound, Mr. Albrecht Bethe 1 Op. cit. p. 62. 1 Fauna, p. 68. ' Cornte. Sue. (1844), p. 34. 4 At least when asked by Dr. H. C. Williamson for the record on which my statement in the History of Crustacea (1893), p. 60, was founded, I was unable to give him any reference for it. 5 Fauna, pp. 69-70. 6 ' Revision,' pp. 12-13. 7 Brit. Stalk-eyed Crustacea, p. 59. 8 Bull. Mus. Comp. Zool. Harvard (1881), viii, p. 257. 9 Journ. cf Marine Zoology and Microscopy (1897), No. 8. 10 Rep. andTrans. Penzance Nat. Hist. Soc. (1890-91), p. 271. 260
