136 MORPHOLOGY OF INVERTEBRATE TYPES 



The carapace is produced anteriorly into a sharp median 

 process or rostrum extending far beyond the eyes. A median 

 longitudinal absorption line which has an important relation to 

 the moulting process runs from the end of the rostrum to the 

 posterior edge of the carapace. Halfway between the rostrum 

 and the posterior edge is a transverse cervical groove between two 

 triangular spots. These spots represent the attachment points 

 of muscles the other end of which is attached to the wall of the 

 gill chamber; the cervical groove itself serves for the attach- 

 ment of the posterior gastric muscles. Beyond the triangular 

 spots the cervical groove continues on each side of the carapace, 

 ending at its anterior edge below the second pair of antennae. 

 Halfway between the triangular spots and the rostrum are two 

 oval tendon marks of tendons which bind the carapace to the 

 endoskeleton. Two depressions called branchiocardiac lines 

 run from the triangular spots toward the posterior edge of the 

 carapace. The region between these lines is called the areola 

 or cardiac region. The region in front of the cervical groove 

 is called the gastric region since the stomach of the lobster occu- 

 pies almost all the space under this region of the carapace. The 

 sides of the carapace, limited dorsally by the cervical and bran- 

 chiocardiac lines, are called the branchial regions. Since the 

 carapace in this region forms merely a protective covering for 

 the gills, the sides of the carapace are called the branchiostegites. 



The abdomen is composed of seven distinct segments of which 

 only the tergites and the lateral lobes or pleura are visible. The 

 appendages of the sixth abdominal segment form together with 

 the seventh abdominal segment a powerful tail-fan used in 

 swimming. A uropod or appendage of the sixth abdominal 

 segment consists of a protopodite or basal joint, a single-jointed 

 cndopodiic, and a two-jointed exopodite. The seventh abdominal 

 segment is called the telson. 



In the position in which the lobster is being examined, several 

 pairs of appendages belonging to the cephalothorax are visible. 

 These are: first and second pair of antcnncc, third maxillipeds, 



