Vol. 52.] ANNIVERSARY ADDRESS OF THE PRESIDENT. ClX 



warped and distorted from their natural shape, by their mode 

 of life, and lose the use of certain members, which cease to 

 grow, while others develop peculiarities in structure, or they may, 

 as in the Soldier-crabs, lose the hard coverings to their bodies. 

 * Dromia does not carry about with it a turbinated shell, like 

 Pagurus, but clothes itself in the bright skin of its victim, a sea- 

 lemon (Doris), for example, or encourages a parasitic sponge of 

 showy colour to grow upon its back, holding it in its place with 

 its two hind pairs of rudimentary feet, just as the other true 

 hermit-crabs hold their shells on over their soft-skinned bodies ' 

 (Gosse). 



Species of Dorippe from Singapore have been observed by 

 Dr. Archer, carrying the leaf of a mangrove-tree over their backs, 

 or the half of a dead bivalve shell, to conceal them from view. 



Specimens of Hyas not only dress themselves in living seaweeds, 

 which they deliberately plant upon their backs, but if their 

 surroundings be changed they will remove these, and replace them 

 with some others more suitable in colour — to match with their new 

 conditions. 



In those forms which, like Hippa, Ranina, Zanclifer, and others, 

 are expert diggers, the body and legs are both specially modified, 

 enabling the animal to sink down rapidly backward into the wet 

 sand, or soft mud, and so escape from capture. 



Fossil Forms. — Of some of the oldest forms referred to this 

 division there is considerable doubt, owing to want of more com- 

 plete fossil evidence. 



Thus, it is not easy to determine the true nature of the genus 

 Oonocarcinus, of which Prof. Gemmellaro has figured and described 

 three species from the i^swZma-Limestone of Palermo, Sicily. 



With these doubtful forms is associated another, named Para- 

 prosopon Meussii, Gemm., which is certainly referable to the genus 

 Cyclus. 



It is possible that Oonocarcinus may be part of an Arachnid, a 

 supposition which its ornament suggests. This is certainly the case 

 with regard to a supposed Brachyurous Crustacean, described by me, 

 in 1878, under the name of Brachypyge carbonis, from the Coal 

 Measures of Mons, Belgium. It proves to be almost certainly the 

 abdomen, not of a Crab, but of an Arachnid near to Eophrynus 

 Prestvici, H. Woodw., from the Coal Measures of Dudley (Geol. 

 Mag. 1871, p. 385). 



In 1866 I had the pleasure of describing a short-tailed crab, 



