FAMILIES OF CARIDEA 163 



Tribe 4. Caridea. 



The third legs are not chelate. The third maxillipedes are 

 4-6 jointed, the end-joint of the second maxillipede nearly always 

 lies as a strip along the end of the joint before it, and the first 

 maxillipedes have a lobe on the base of the exopodites. The pleura 

 of the second abdominal segment overlap those of the first. 'The 

 abdomen has a sharp bend ; the branchiae are phyllobranchs. 



Fam. 1. Pasiphaeidae. In this family the end-joint of the 

 second maxillipedes is normally formed, and exopodites are usually 

 present on all the thoracic liinbs. Eostrum small or wanting. 

 Bather numerous genera are known, most of which inhabit the 

 deep sea, though a few come into the littoral zone. Pasiphaea 

 chiefly in the deep sea, Leptocliela, in the tropical littoral zone. 



Fam. 2. Acanthephyridae. The end-joint of the second 

 maxillipede is modified as in other Caridea, and the rostrum is 

 very strong and serrate, but in the presence of exopodites, and in 

 the form of the mouth-parts, this family agrees with the pre- 

 ceding. It is also a characteristic deep-sea family. Acanthe- 

 pliyra, Hy menodora,, Nematocarcinus, etc. 



Fam. 3. Atyldae. This is an entirely fresh-water family, 

 especially characteristic of the rivers and lakes of the tropics, 

 some of the forms being exceedingly large and taking the place 

 of the Crayfishes in these waters. Characteristic of this family 

 is the fact that the fingers of the chelae are spoon-shaped, and 

 cany peculiar tufts of bristles. Exopodites are present on the 

 thoracic limbs of some of the genera (Troylocaris, Xiphocaris from 

 Australia and the Malay Islands, Atyephyra from S. and AY. 

 Europe), but are absent in others. Caridina, widely spread and 

 common in Indo-Malay and Africa ; Atya from West Indies, West 

 Africa, and Pacific Islands. 



Fam. 4. Alpheidae. 1 The exopodites are absent, and the 

 rostrum is absent or very feeble. The chelae are powerful, and 

 usually very asymmetrically developed. Alplieus has an enormous 

 number of species which live chiefly in the tropical seas, where 

 they haunt especially the coral-reefs, making their homes among 

 the coral or in sponges, etc. Although occurring in the Mediter- 

 ranean they penetrate very rarely into colder seas. 

 1 Coutiere, Fauna and Geoyr. Maldive and Laccadive Archipclayos, ii., 1905, p. 852. 



