92 GUIDE TO THE AUSTRALIAN MUSEUM. 



Sub-class L— ENTOMOSTRACA, is represented by the 

 order Pliyllopoda, whose species are mostly inhabitants of fresh 

 water, and liave bodies composed of many segments; they have leaf- 

 like swinnning feet, and a shield-like carapace, or in some 

 representatives a laterally compressed bi- valve shell. Lepidurus 

 viridis from Tasmania, and several species of the genus Apus 

 from N. S. Wales, are examples. (See Case 17.) 



Sub-class II.— XYPHOSURA or King Crabs, contains but 

 two known species, both of which are represented in the collection, 

 viz : Liinnlus polyphemus from North America, and L. longisjnna 

 from the straits of Malacca. The body is covered by a large 

 siiield-like carapace, and the abdomen ends in a long spine-like 

 tail. (See Case 17.) 



Sub-class III.— EDRIOPHTHALMA, or sessile-eyed 

 Crustacea, contains two orders : — (See Case 12.) 



1. Amphipoda, in which the branchise consist of mem- 



branous vesicles at the bases of the legs. The thorax has 

 six or seven free segments, and the abdomen seven segments, 

 the terminal segment being adapted for swimming. Ex- 

 amples — Orchestia tnacleayana^ and LeucotJioe novce- 

 hollandicb. 



2. Isopoda. — In this order the body is broad and depressed ; 



the head is distinct from the thorax ; the latter consists of 

 seven free segments, each bearing a pair of legs, all, except 

 the first pair being alike ; the branchial lamellae are placed 

 under the abdomen. Examples — Idotea excavata, Forcellio 

 obtusifrons, Sphceroma Iwvis, and Gyinodocea puhesce7is. 



Sub-class IV. — PODOPHTHALMA or stalk-eyed 

 Crustacea, includes the shrimps, lobsters, crayfishes, and crabs. 

 These are characterised by having their eyes on movable stalks, 

 and by the head being more or less fused with the thoracic segments, 

 forming the carapace which covers and protects the body. In the 

 order Stomatopoda the branchiae are external, and are usually 

 attached to the under surface of the abdomen ; the latter is 

 elongate, and ends in a powerful tail, which is the chief organ of 

 locomotion. Examples — Lysiosquilla brazieri, Squilla miles, and 

 Gonodactylus cldragra. (See Case 12.) 



