80 A HISTORY OF RECENT CRUSTACEA 



In the last four genera it will be perceived that the 

 maxillipeds do not form a completeoperculum,but by the 

 arrangement of the inner edges of their third and fourth 

 joints they leave a lozenge-shaped space over the mouth- 

 opening uncovered, while in Uca and Gecarcinucus the 

 straight inner edges from either side can be brought exactly 

 together so as to close the cavity completely. Mr. Wood- 

 Mason points out that the character of the exopod distin- 

 guishes Gecarcinus, Gecarcoidea (which he calls Pelocar- 

 cimts), and Hi/lceocarcinus from the three preceding genera, 

 and that they are distinguished from one another by a 

 further character of the maxillipeds, for in Gecarcinus the 

 three terminal joints are completely hidden, in Hylceocar- 

 cinus they are partially visible, and in Gecarcoidea com- 

 pletely so. 



None of the Crustacea have more attracted the atten- 

 tion and excited the wonder of travellers than some of 

 those belonging to this group. Like the twin snakes that 

 came over the sea and deliberately landed at Troy to slay 

 Laocoon and his two sons, these crabs have, contrary to 

 nature, forsaken the ample waters of the ocean, scorned 

 all the brooks and rivers and lakes, and carried out a 

 portentous invasion of the dry land. Still they are by no 

 means indifferent to moisture. The vaulted part of the 

 carapace over the branchial regions is lined with a very 

 spongy membrane, and sometimes a fold of the membrane 

 along the lower edge of the cavity forms a kind of tube in 

 which water may be held as in a reservoir. But their 

 form and structure are not so surprising as their manners 

 and customs. 



Under the heading Cancer ruricola, a species of Geccw- 

 cinus, Herbst brings together many curious particulars, 

 depending largely upon Patrick Browne's ' History of 

 Jamaica.' In the Bahamas, he says, and in tropical 

 regions these land-crabs are so numerous that when they 

 creep out of their holes the ground seems to be in motion. 

 One little island is so full of them that it has been called 

 Crab Island. They are just as frequent in certain districts 

 of Jamaica and in some of the Caribbee islands. The same 



