LONG-TAILED GROUP 3229 



species of the latter genus occur in British waters, but the majority of the Oxysto- 

 mata are inhabitants of the Tropics. In the genus Dorippe, belonging to the family 

 Dorippidce^ the last two pairs of legs are short and raised on the upper surface 

 of the body behind the carapace. In this position and structure they are adapted 

 for carrying foreign bodies to serve as a protection. 



The aberrant forms constituting the tribe Anomala differ from the other mem- 

 bers of the suborder in having sometimes as many as fourteen pairs of gills, 

 and also in that the apertures of the oviducts are situated upon the basis of the third 

 pair of legs and not upon the breast plate of the cephalothorax. Moreover, as in 

 the Dorippidce of the preceding tribe, the last or last two pairs of legs are shorter 

 than the rest, and dorsally placed, as shown in the illustration of the common 

 Dromia vulgaris. The crab uses these limbs to hold foreign bodies like sponges 

 and shells beneath which it thus lies concealed. 



GROUP SUBORDER Macrura 



This suborder, comprising the lobsters, hermit crabs, prawns, and shrimps, is 

 distinguished by having the abdomen or tail usually of large size, and constituting 

 a powerful flapper for swimming, in which function it is assisted by the 

 enlargement of the appendages of its last segment to form with the telson a power- 

 ful tail fin. The external maxillipedes are slender and leg-like, and the antennae 

 usually longer than the body. The first tribe, Anomura, contains forms which 

 typically have a symmetrical tail. With these were originally classified the 

 anomalous crabs, and there is no doubt that some of the species bear a striking 

 resemblance to the latter. This is shown in the illustration of the broad-clawed 

 porcelain crab {Porcettana platycheles) , which frequents 

 rocks and seaweed at low water. It may be distinguished 

 from the true crabs by its long antennae, the presence 

 of a tail fin, and the slender unflattened exteral maxil- 

 lipedes. The most familiar members are the hermit 

 crabs, which abound in all seas, and are represented by 

 several British species. In the typical forms the integu- 

 ment of the abdomen is soft; and aware of its defenseless- 

 ness, the hermit crab invariably thrusts itself for protec- BROAD-CLAWED PORCELAIN 

 tion into some empty shell, which it subsequently never CRAB (natural size), 

 willingly quits, save for the purpose of changing its abode 



for a larger one, when compelled by the exigencies of growth. It is not an uncom- 

 mon thing to find shells containing a hermit crab surmounted by a large anemone. 

 The advantage to the crab of this association is considerable, for anemones are so 

 distasteful that no fish will bite at them twice, and consequently a fish that would, 

 under ordinary circumstances, greedily swallow a hermit crab, shell and all, will 

 not so much as sniff at it if protected by an anemone. One of the commonest deep- 

 water British hermit crabs, Eupagurus prideauxi, is invariably found associated 

 with an anemone, but the latter adheres to the lower surface of the shell in such a 



