A HISTORY OF CORNWALL carapace than is found in the first and larger species. It may be questioned whether this contri- butes more than a variety, and whether the variation itself may not be one that disappears from specimens which attain a large size. Bell says that Mr. Couch sent it him from Cornwall, but does not specify whether he is referring to the father or the son, both of whom were his correspondents. 1 The genus is distinguished from B/astus by the widened second joint of the outer antennae and by having the fingers of the walking legs smooth instead of pectinate. Blastus tetraodon (Pennant), the ' Four spined sea-spider,' is marked by Couch as ' not common,' 8 and by Cocks as found in ' Carrack Roads, east of lighthouse, trawl refuse ; rare.' B. tribulus (Linn.) is perhaps the same as Arctopsis lanata, Lamarck, under which name Cocks records it from ' Harbour, Carrack Roads, east of lighthouse, trawl refuse, etc. ; not uncommon.' It is the Cancer biaculeatus of Montagu, the Pisa gibbsii, which Leach describes as not an uncommon species on the southern coast of Cornwall, inhabiting deep water, and taken by the trawl net, 3 and which, under the name of ' Gibbs' sea- spider ' Couch notes as ' not uncommon in from one or two to twenty fathoms of depth, and taken in crab-pots.' 4 Of the four strong lateral teeth in B. tetraodon only the lowermost is well represented in B. tribulus, the male of which is also well distinguished by the rostrum, for this is about the length of the rest of the carapace, instead of being only about a third as long, and its two horns are scarcely at all divergent at the apices. Eurynome aspera (Pennant), at one ,;'>--> referred to the Parthenopidae, has after the fashion of that family a coat rugged with tubercles, and in the males the chelipeds much longer than the following legs. Couch apparently had not seen this little species at Polperro and marks it ' rare.' 6 Leach reports it as found by dredging in deep water on the coast of Cornwall and neighbouring counties, and figures specimens sent him by his ' very industrious friend, C. Prideaux, Esq., who obtained them from the trawl-fishers of Plymouth Sound.' He adds that ' many of the tubercles on the back of the shell have a cauliflower sculpture.' e Cocks records it ' under stones, low-water mark, Gwyllyn-vase ; scarce. Trawl refuse, etc. ; common.' The family Mamaiidae is here represented only by the genus Mamaia, a name which must supersede the preoccupied and otherwise untenable Mala of Lamarck. 7 The orbits are deep and fenced with spines, one of which belongs to the broad base of the outer antennae. Leach says that M. squinado (Herbst) ' is extremely common in deep water off the south-western coasts of Devon and Cornwall, being called by the fishermen King-crab or Thorn-back.' 8 Couch calls it ' Corwich crab or Skerry,' and says ' this in its season is the most abundant species of the family, and by far the largest, sometimes weighing as much as five pounds, and the carapace measuring nine or ten inches in length ; so that it is commonly used as food, though only by poor people and fisher boys, who find it a delicate meal. Its not tempting form and the small size of the legs conspire to exclude it from the tables of the rich.' 8 Many interesting remarks on this species from the pen of Mr. Richard Couch are quoted by Bell, 10 and these are repeated by Bate in his revision of Couch's Cornish Crustacea as though they had been written by Mr. Jonathan Couch. Cocks finds the species in ' crab-pots, trawl refuse, etc. ; common.' As distinguished from the six species of Inachidae, the six species of the last two families all have the pleon seven-segmented in both sexes. The Oxystomata furnish Cornwall with three small species all belonging to the genus Ebalia (Leach), in the Leucosiidae. In this family the branchiae are fewer than nine in number on either side, and the afferent branchial channels are found on either side of the endostome or buccal cavity, the efferent canals in Oxystone crabs not lying at the sides but traversing the endostome in the middle line. 11 Ebalia tuberosa (Pennant), E. tumefacta (Montagu), and E. crancbii, Leach, all are recorded by Cocks from ' trawl refuse ; not uncommon.' Couch had himself only met with the second. Of this Leach says, ' I have obtained it from the Sound of Plymouth through the liberality of Mr. C. Prideaux. I have seen but one male, which differs from the female in not having the dorsal tubercles tumid.' 12 Of his own E. cranchii. Leach says, ' this species was discovered by that enterprizing naturalist Mr. J. Cranch (whose death in the late expedition to Congo has been so much lamented by naturalists), in the sound of Plymouth, where Mr. C. Prideaux has likewise observed it, in considerable plenty, and has supplied my collection with a complete series.' 13 Leach and Bell agree that in E. tuberosa the pleon has the third to the sixth segments united, that in E. cranchii the third to the fifth are united in the pleon of the male, and that the fourth to the sixth 1 Brit, Stalk-eyed Crustacea, p. 36. ' Fauna, p. 65. 3 Make. Podophth. Brit. (1815), text to PI. XIX.I 4 fauna, p. 65. 4 Ibid. e Malac. Podophth. Brit. (1815), text to PI. XVII. 7 See Stebbing, South African Crustacea, pt. iii, p. 22 (1905). 8 Malac. Podophth. Brit. (1817), PI. XVIII. " fauna, p. 66. 10 Brit. Stalk-eyed Crustacea, p. 42. " See Alcock, Indian Decapod Crustacea (1901), pt. i, p. 19. " Malac. Podophth. Brit. (1817), text to PL XXV. 13 Ibid. 264
