MICHIGAN ACADEMY OF SCIENCE. 69 



2. fc«lmall eiitomosti-aca liaviug- body completely inclosed in a bivalved 



carapace, formed of articnlated right and left valves; body im- 

 segmented; abdomen rndimentary ; only seven pairs of append- 

 ao-es Order OsHracocki, p. 71. 



3. Small entomostraca, having- an elongated body which is usually dis- 



tinctly segmented; thorax bears three or four pairs of biramous 

 appendages, abdomen has none; many are parasitic and show 

 various stages of degeneration of structure. Order C'ope^jOfZo, p. 71. 



a. Free living forms; eggs develop in a brood sac attached to 

 the abdomen ^ Sub-order Eucopepoda, p. 71. 



b. Ectoparnsitic forms; body strongly depressed; no brood 

 sacs Sub-order Branchiura^ p. 72. 



• 



KEY TO ORDERS AND SUBORDERS OF MALACOSTRACA. ' 



1. Small and shrimp-like; thorax covered by a soft carapace; thoracic 



appendages all biramous; eyes stalked. . . .Order Mysidacea, p. 73. 



2. Head and thorax united to form a cephalothorax which is covered by 



a carapace; three anterior pairs of thoracic appendages form bi- 

 ramous foot jaws, the posterior five pairs of walking legs are un- 

 iramous ; eyes stalked Order Decapoda, p. 73. 



3. No carapace/ the first and sometimes the secoud thoracic segment 



fused with the head, the remaining seven are free; eyes 

 sessile Order Artlirostraca, P- 73. 



a. Body compressed, or flattened from side to side. 



Sub-order, Amphlpoda, p. 73. 



b. Body depressed, or flattened from above downwards. 



Sub-order, Isopoda, p. 73. 



Order Phyllopoda. 

 Sub-order Euphyllopoda. 



* 1. Branchipus rentalis Yerril 



This species was taken throughout the springs of 1909 and 1910 at 

 White's Woods near Ann Arbor. 



Sub-order Cladocera. 



2. Acroperus leiicoceplialus Koch 



Marquette (Forbes, '91), Lake St. Clair (Reighard, '91). 



3. Alona affinis Leyd. 



Lake St. Clair (Reighard, '94). 



4. Alona guttata Sars 

 Lake St. Clair (Reighard, '94). 



5. Alona lineata Fischer 

 Lake St. Clair (Reighard. '94). 



6. Alona qudranytilaris Miiller (=^1. ohlonga P..E. Mueller). 

 Marquette (Forbes, '91). 



7. Alonella rostrata Koch 

 Lake St. Clair (Reighard. '94). 



8. Bosniina lonfjirostiis O. F. M. 



