38 Guide to Crustacea. 



Table-case This division includes, among living Crustacea, a small number 

 No. 5. Qf very peculiar forms recently discovered in the fresh waters of 

 Tasmania and Victoria (Fig. 16). They are of special interest on 

 account of the fact that they appear to be survivors of an ancient 

 gi'oup of Crustacea of which the remains are found fossil in Car- 

 boniferous and Permian rocks. The drawing of the fossil Prac- 

 anaspides praccursor (Fig. 17), exhibited in the case, shows the 

 great resemblance in general form between that species and the 

 recent Anaspides (Fig. 16). 



Division 3.— PERACARIDA. 



The carapace, when present, does not coalesce dorsally with 

 moi'e than four of the thoracic somites. The eggs and young are 



Fig. 18. 



Mysis relicta, female, from the side, c.s., " Cervical groove " ; vi., Brood- 

 pouch. (From Lankester's " Treatise on Zoology," after Sars.) 



carried in a brood-pouch formed by overlapping plates attached to 

 the bases of the thoracic limbs. 



The following Orders are included in this division : — 



Order 1. Mysidacea. 

 ,, 2. Cumacea. 

 ,, 3. Tanaidacea. 

 ,, 4. Isopoda. 

 ,, 5. Am]>liij)()d(i . 



Order 1. — Mysidacea. 



The general form is shrimp-like (Fig. 18). A carapace is 

 present, but it leaves free at least live of the thoracic somites. 



