I 64 CRUSTACEA—EUCARIDA—DECAPODA CHAP. 
Fam. 5 Psalidopodidae.—This family, characterised by the 
absence of chelae on the second thoracic lmbs, 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 thoracie 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. acwminatus, 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.’ 
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 and 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) 
iid: NOLO lyphoorungon “apinutesin with numerous species entirely con- 
from the right side, x. (From fined to deep water. 
Sees oo prepared for 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., excvi., 1904, p. 295. In the young 
a constant and very simple chromatophore-system is present, but in the adult a 
