' LOBSTEE OR CEATFISH 141 



taken as typical, with its appendages, remove the 

 contents of the " shell," and note 



The segment proper. — What is its shape as seen 

 from the end ? From the side ? How is the 

 cuticular covering or exoskeleton modified in dif- 

 ferent places ? Make out the following regions 

 on the segment : 



1. The tergum, or dorsal portion of segment. — 



What is its shape ? Structure ? Color ? What 

 differences between its anterior and posterior 

 edges ? 



2. The sternum, or ventral portion of segment be- 



tween the appendages. — Shape? Size as com- 

 pared with the tergum ? Structure ? Color ? 



3. The epimeron, or latero-ventral portion of seg- 



ment external to appendage. — Shape ? Of what 

 is it composed ? Color ? 



4. The pleuron, or downgrowth of the side of the 



segment. — Shape? Size? Structure? Color? 

 Differences between anterior and posterior mar- 

 gins ? What relation does the anterior margin 

 bear to the preceding segment ? 



Near the points of union of the tergum with 

 the pleura find 



5. The articular facets. — What is their shape? Of 



what are they formed? How many are there 

 on one segment ? What relation do they bear 

 to the preceding segment ? 



The appendages or " S"wininierets."^How many 

 on the segment ? What is their position ? Color ? 

 How are they attached to the segment ? Make 

 out the following parts on each appendage : 



