MARINE MISCELLANEA. 239 



entering the tropics, the large Mangrove Crab, Scylla serrata, almost equal in 

 dimensions to the British " Parton," becomes fairly plentiful, and is held in high esteem. 

 As its popular name implies, the favourite haunt of this crab is the dense mangrove 

 thickets, wherein it excavates deep burrows, from which the experienced fisherman is 

 wont to dislodge it with a long hooked wire. 



Apart from the economical varieties, Australian waters produce an infinity of bizarre 

 Crustacean types. Not the least notable among these are the relatively small mangrove- 

 frequenting crabs belonging to the genus Gelasimus. As many as seven species have been 

 recorded as inhabiting Australia. They all share the same eminently gregarious habits, 

 forming regular warrens with their associated burrows on the sea-shore, or more commonly 

 among the mangroves. The special structural distinction of the members of this genus 

 is the huge relative size of one of the larger fore-claws, or " chselce," of the male 

 individual. Sometimes it is the right and sometimes the left claw which exhibits this 

 abnormal development ; though, as shown in the photographs of one of the most con- 

 spicuous North Australian species, reproduced on the following page, in as many as 

 five out of six of the crabs figured, this larger chaela is the left one. The particular 

 species, Gelasimus coarctata, here portrayed, is remarkable for its brilliant colouring, 

 as well as for its grotesque shape. Except the back of the carapace, which is 

 glossy black, the huge claw, the under surface, and all the other limbs are a most 

 brilliant scarlet vermilion, inclining to crimson. The aspect, in fact, of a number 

 of these crabs seen from a little distance, as they lie stationary at the mouths 

 of their burrows, against the dark background of mud and mangrove, is that of hot, 

 glowing coals. Presently one of these living coals will move out towards another one. 

 It is the literal carrying of a firebrand into the enemy's camp. The two presently become 

 engaged in a deadly combat, there is a rapid retreat of the vanquished warrior, and 

 he disappears into his hole like an extinguished spark. Advance a step nearer, and 

 the whole community as suddenly and simultaneously vanish, leaving the spectator in 

 possession of the seemingly utterly barren and untenanted mud-flat. If he stands still for 

 a brief interval, they one by one re-appear at the mouths of their burrows and illumine 

 the landscape with their glowing tints. In the third figure, from the top of the group 

 here portrayed, a male crab of this species is represented very nearly the natural size. 

 The female is somewhat smaller, and possesses two very tiny pincers, as homologues 

 of the large and little claw of the male. Two examples of this relatively unarmed sex 

 may be readily identified in the lower portion of the accompanying illustration, one 

 of them occupying a position immediately above the two champions fighting in the left- 



