i'L 



Guide to Crustacea. 



Table-case PodoplitJialuiiis viijil (Fig. 48) is remarkable for the great length 

 No. 15. Qj[ ^YiQ eye-stalks, which is quite unusual among the Cyclometopa, 

 and gives this Crab a curious likeness to the genus Macroph- 

 thahnus among the Ocypodidae {see Table-case No. 16). Tiie 

 resemblance, however, is quite superficial, for in this case it is the 

 first of the two segments of the eye-stalk which is elongated, while 

 in Macrophihahmis it is the second. 



The genus Platyonychns, of which a group of specimens is 

 mounted in Wall-case No. 5, also belongs to this family. 



The Cancridae are distinguished from the preceding families by 

 having the antennules folded longitudinally instead of transverselv. 



Fig. 48. 



T'dili/ilillKiliint-'i r\(jU (reduced). FTable-case No. 15.] 



To the typical genus Cancer belongs the Edible Crab of British 

 coasts, of which a large specimen is exhibited in Wall-case No. 5. 

 The wide distribution of the genus is illustrated by species from the 

 Azores and from New Zealand. 



The family Potamonidae^ (Tlielpliusidde) comprises the Eiver- 

 Cral)s. In the shape of the carapace, which is generally more or 

 less square, and in having the front bent downwards, these Crabs 

 show some resemblance to the next Tribe, Catometopa. They are 

 widely distributed in fresh waters throughout the Tropics. Potamoii 

 edulc (better known as Thelphiisn Jlii7-i<itilis) occurs in Italy and 

 other parts of Southern Europe. 



The family Corysddae includes Cnibs which are allietl to Ihe 

 Canci-idae, but have long aiiteiniae, and the third niaxilhpeds are 



