DECAPOD A. MACRUBA NATANTIA. 533 



according to the number of which the family is subdivided as follows : 

 (a) 2 joints. Caridion Goes, Eur. (6) few jointed. Virbius and Ogyris 

 Stimpson, with long slender eye stalks, 3 spp. E. Asia and W. Indies. 

 Pterocaris Heller. 1 sp. Amboyna. Cephalo -thorax and the 3 ant. fused 

 abdominal segments expanded into lateral wings, (c) 7-many jointed. 

 Hippolyte Leach, many spp. widely distributed over the world. H. varians 

 Leach, British, common in tidal pools, has the power of changing its 

 colour according to its surroundings (p. 444). Spirontocaris, Merhippolyte, 

 Chorismus, Hetairus of Sp. B., Saron Thallwitz, and Hetairocaris de 

 Man. Nauticaris Sp. B. ; Platybema Sp. B. ; Concordia Kingsley ; 

 Latreutes Stimps. ; Tozeuma Stimps. ; Lysmata Riss. Cryptocheles and 

 Bythocaris, from great depths, the young being hatched with the full 

 number of appendages, were described by G. O. Sars, but are regarded 

 as doubtful genera by Ortmann. 



Fam. 10. Rhynchocinetidae. Closely allied to Hippolyte but the 

 rostrum is articulated with the carapace, and the 2nd trunk -leg has the 

 carpus not articulated. Rhynchocinetes M. Edw. 



The two following families form an oft'-shoot from the Hippolytidae, 

 characterized by having the blade of the mandible divided, the two 

 anterior pairs of trunk-legs chelate, the second larger than the first, and 

 the carpus not articulated, no epipodites on the trunk-legs, and the first 

 antennae often 3-ramous. 



Fam. 11. Pontoniidae. Rostrum broad at base; 1st antenna split 

 at the tip ; palp of mandible usually 0, 3rd maxilliped pediform, broad 

 at the base (opercular) ; 2nd trunk-legs unequal, one very large in male. 

 Littoral forms, often half parasitic, (a) mandible without palp. Pontonia 

 Latreille. P. custos Forsk. lives between the valves of the shell of Pinna ; 

 P. meleagrinae (Pet.) in the Pearl Oyster. Typton Costa. T. spongicola 

 Costa, lives in sponges ; British. Anchistia Dana, A. lacustris v. Mart. 

 fresh-water, Italy. Coralliocaris Stimpson, Ind. Pac. (6) Rostrum com- 

 pressed ; 1st antenna expanded into a flattened lobe ; 3rd maxilliped 

 with leaf -like flattened joints, mandible with palp. Hymenocera Latreille, 

 Ind. Pac. 



Fam. 12. Palaemonidae. Rostrum large, compressed, serrated ; 1st 

 antennae with 3 flagella ; palp of mandible usually present ; 3rd maxilli- 

 ped leg-like. Leander Desm. (Palaemon Fabr. pars). L. serratus (Fabr.) 

 the prawn of the markets. Palaemon Fabr. pars, 2nd trunk-legs much 

 elongated, especially in the male, tropical fresh-waters. P. heterochirus 

 Wiegman, of Mexico, 2 feet long including the legs. P. potiuna hatches 

 with the appendages of the adult, except the uropods (Fr. Miiller). 

 Palaemonella Dana. Palaemontes Heller. P. varians (Leach). Fresh and 

 salt water. It has been found that while N. European forms of this species, 

 living in the sea and brackish water, hatch in the usual zoaea form 

 (Boas), S. European specimens inhabiting streams have, at hatching, all 

 the appendages except the uropods, and only the two anterior pairs of 

 trunk-legs bear exopodites (P.- Mayer), the metamorphosis of the fresh- 

 water form being abbreviated: 



The 3 following families form an offset from the Hippolytidae in another 

 direction, characterized by having the blade of the mandible simple, and 

 its palp absent, the inner lobes of the 2nd maxilla much reduced, and no 

 epipodites on the trunk-legs. 



Fam. 13. Processidae (=Nikidae). Rostrum flattened above; 3rd 

 maxillipeds slender ; 1st trunk-legs either chelate on one side only (Processa), 



