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. 



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