164 



CRUSTACEA EUCARIDA DECAPODA 



Fam. 5 Psalidopodidae. This family, characterised by the 

 absence of chelae on the second thoracic limbs, which carry 

 instead a terminal brush of hairs, and by the rudimentary con- 

 dition of the eyes, is represented by the genus Psalidopus from 

 the deep waters of the Indian Ocean. 



Fam. 6. Pandalidae. The first thoracic limb is without 

 chelae, only six-jointed. The rostrum is large and toothed. The 

 genus Pandalus has numerous representatives in the northern 

 littoral, P. annulicornis being one of the prawns most commonly 

 met with in the fish -markets. 



Fam. 7. Hippolytidae. The first and second thoracic limbs 

 bear chelae, the carpus of the second being divided into two or 

 more segments. The first pair of chelae are not , distinctly 

 stronger than the second. Virbius has many species in the 

 littoral zone of all seas, and one species, V. acuminahis, is 

 pelagic. Hippolyte also has numerous littoral forms distributed 

 all over the world, but chiefly in the arctic or subarctic seas. H. 

 varians, common on the English coasts, shows interesting colour- 

 reactions to its surroundings. 1 



Fam. 8. Palaemonidae. The 

 first two pairs of legs are chelate, 

 the carpus of the second not being 

 subdivided. Palaemon serratus, a 

 very common prawn in the British 

 littoral. Palaemonetes in the brack- 

 ish arid fresh waters of Europe and 

 N. America. 



Fam. 9. Glyphocrangonidae. 

 The first pair of legs are sub- 

 chelate, the carpus of the second 

 pair is subdivided, and the rostrum 

 is long. Glyphocrangon (Fig. 110) 

 . , with numerous species entirely con- 



FiG. 110. Glyphocranyon spmulosa, J 



from the right side, x 1. (From fined to deep Water. 



pVSrwirr " P Fam. 10. Crangonidae.-The 



first pair of legs are subchelate, the 



carpus of the second pair is not subdivided, and the rostrum is short. 

 Crangon vulgaris is the common Shrimp of the North Sea. 



1 Keeble and Gamble, Phil. Trans. Ser. B., cxcvi., 1904, p. 295. In the young 

 a constant and very simple chromatophore-system is present, but in the adult a 



