CRUSTACEA— MALACOSTRACA. 



383 



XIII. Mesothyra Hall and Clarke. 

 Large; valves of carapace Interlocking at contact of two sub- 

 triangular projections of dorsal line opposite the eye lobes, leaving 



Fig. 1689. Mesothyra oceani, outline of carapace, and abdomen and telson, X Yz- 

 (After Hall and Clarke.) 



a broad anterior and long posterior cleft, closed by median plate; 

 with strong lateral carinae which are crenulated at the summit; 

 posterior margin produced in a conspicuous spine ; two broad seg- 



