300 TRANSACTIONS LIVERPOOL BIOLOGICAL SOCIETY. 



postero-lateral ridge, which is continuous on its outer side 

 with the antero-lateral border. At its outer edge it is 

 coincident with the postero-lateral border, but as it passes 

 inwards it becomes quite distinct from the latter and 

 dies away near the median line in front of the posterior 

 border. 



The Posterior Border of the carapace ^horizontal, 

 and is continuous behind with the tergum of the first 

 abdominal segment. 



Areas of the Carapace. (Text fig. 2.) 



The dorsal surface of the carapace is divided up by 

 means of small depressions into areas. 



The Cervical groove (C. gr.) separates the cephalic 

 region of the carapace from the thoracic region. This 

 groove is seen as a transverse median depression a little 

 more than half way down the carapace. The width of this 

 median groove is almost equal to the distance between the 

 two supra-orbital lobes. 



At each of its outer edges the median groove is 

 continuous with a well-marked depression which 

 commences at the posterior end of the fifth lobe of the 

 antero-lateral border. This depression is curved, the 

 convexity being in front. The median groove and its 

 two lateral extensions together form the cervical groove. 



The Cejmalic portion of the carapace is divided into 

 the Facial and Gastric regions. 



The Facial region is separated from the rest of the . 

 cephalon by a faint transverse depression near the front 

 of the carapace. The outer ends of the depression bend 

 forward and terminate on the second lobe of the antero- 

 lateral border. This region is divided into a median 

 Frontal region (Fr.) and two lateral Orbital regions (Orb.). 



The Gastric region is bounded behind by the 



