LONG-TAILED GROUP 



3237 



presses into pellets, and transfers to its mouth. The two small Crustaceans figured 

 in the illustration belong to the family Pontoniidcz. Both are semiparasitic in 

 habits, Pontonia living between the valves of mussel shells, and Typton being a 

 lodger in sponges. 



The Polycarpinea contains those 

 species in which the wrist of the second 

 pair of trunk legs is divided into several 

 secondary segments. In other respects 

 they are nearly allied to the last group. 

 A common British representative is the 

 red shrimp {Pandalus montagui), which 

 gives its name to the family Pandalidce, 

 and is abundant upon many parts of the 

 British coasts. This tribe is abundantly 

 represented in tropical seas by the hooded 

 shrimps (Alpheidce*) , remarkable for the 

 concealment of the eyes beneath the 

 edge of the carapace, and for the enor- 

 mous size, bright colors, and peculiar 

 shape of the right or left pincers. 

 With this instrument the hooded 

 shrimps, which frequent holes and 

 crevices in the coral reefs, are able to 

 produce a clicking sound when angry 

 or alarmed by the approach of danger. 

 The last tribe of the suborder, known 

 as Penseidea, appear similar to the 

 Monocarpinea, but may be distinguished 

 by the circumstance that the first three 

 pairs of trunk limbs are chelate, so 

 that only the posterior two terminate in 

 simple claws. Some of the species of the 

 genus Penczus, belonging to the family 

 Penceidcz, attain a large size in tropical 

 seas, and form an important article of 

 commerce. Nearly allied is the little 

 Spongicola venusta, which makes its 

 home in glass sponges. In this neigh- 

 borhood may be placed the anomalous 

 family, Sergestidce, in which the gills are 

 impoverished or lost, while the first pair 

 of trunk legs and sometimes the second 

 are simple, the chelae of the third are 



minute, and the fourth and fifth pairs 

 are feeble, rudimentary, or absent. To 



LONG-NECKED SHRIMP, Leucifer. 

 (Much enlarged.) 



