DECAPODA. MACRURA NATANTIA. 529 



the two preceding trunk-legs chelate. Abdomen long. The larvae hatch 

 either in the nauplius (Penaeus), metanauplius (Leucifer) or protozoaea 

 (Sergestes) stage. 



Fam. 1. Penaeidae. In most the three anterior trunk-legs retain 

 flagelliform exopodites (as in Schizopods), and an epipodial plate, which 

 is however usually without branchial filaments. They are chelate, 

 and successively increasing in length ; their antepenultimate segments 

 long. The branches of the gills bear multifid or arborescent subdivisions. 

 Rostrum present ; posterior part of abdomen dorsally carinate ; first 

 abdominal segment overlaps the second at the sides. Eye stalks 2 or 

 3-jointed ; mandibular palp broad, 2-jointed. Several Jurassic genera 

 (Boas). Penaeus Fab., flagella of 1st antennae shorter than carapace ; 

 P. caramote (Risso) Mediterranean, occasionally British. P. esculentus 

 Hasw., the edible prawn in Sydney, N.S.W. Penaeopsis Sp. B. 

 Solenocera Lucas, 1st antennae modified to conduct the efferent 

 respiratory water. Parasolenocera W.-M. and A. ; Hymenopenaeus 

 Smith ; Haliporus, Artemesia and Philonicus Sp. B. ; Parapenaeus 

 Smith ; Metapenaeus W.-M. and A. Sicyonia M. Edw., exopodites 

 of trunk -legs absent; littoral. The 6 genera Aristeus Duv., with 

 branchiate epipodites to the 2nd-6th thoracic legs, Aristaeopsis and 

 Aristaeomorpha W.-M. and A., Hemipenaeus and Hepomadus Sp. B., and 

 Benthesicymus Sp. B., inhabit the deep sea. Gennadas Sp. B., also from 

 the deep sea with supplementary lens to the eye. A genus described as 

 Peteinura by Spence Bate hasexopodite of 6th abd. -appendage immensely 

 elongated in larva. 



Here may be mentioned a remarkable form Cryptopus Lat. ( = Cera- 

 taspis Gray) a pelagic Crustacean, 8 mm. long, which has been obtained 

 from the stomachs of fishes (bonito and " dolphin " (Coryphaena)). The 

 carapace is inflated and its sides nearly meet ventrally. Seven biramous 

 thoracic legs are present, bearing at their bases simple or compound 

 phyllobranchiate gills. The nauplius stage is apparently passed before 

 the young escape from the eggs, which are attached to the thoracic legs 

 and sheltered in the carapace. 



Fam. 2. Sergestidae. With elongated bodies and slender limbs. 

 Mandibular palp 2-jointed. 2nd and 3rd maxillipeds pediform. The 

 trunk -legs have lost their exopodites, the epipodites are also absent and 

 the 4th and 5th are reduced or absent. Gills when present, reduced 

 in number, with simple lamellar subdivisions of the branches of the main 

 axis. Chelae of the trunk-legs minute. First abdominal appendages of 

 male modified as copulatory organ. Sergestes M. Edw. Two posterior 

 pairs of trunk-legs reduced. Flagellum of 2nd antennae very long. Arthro- 

 branchiae absent. Stages in the remarkable metamorphosis known as 

 Elaphocaris (protozoaea and zoaea), Acanthosoma (mysis stage) and 

 Mastigopus. Many spp. pelagic, and widely distributed, but one found 

 by Graham Kerr, on the Rio Parana, S. Am., several hundred miles 

 from the sea. Acetes M. Edw. A. indicus M. Edw. Last trunk -legs 0, 

 4th reduced. Mouth of the Ganges. Petalidium Sp. B., arthro branchiae 

 on 5 pairs of anterior thoracic legs. Leucifer M. Edw. Cephalic region 

 and eye-stalks much elongated, and thoracic region very short. 4th and 

 5th trunk -legs 0. Gills 0. Phosphorescent. Young hatched in meta- 

 nauplius stage. The metamorphosis through protozoaea (Erichthina), 

 zoaea, mysis, and mastigopus stages has been followed by Brooks (Fig 

 324). 



Z III M M 



