near the anterior end. Rostrum 7 or 8 dentate above. 



P. monodon. 



II. No tooth on the inferior margin of the rostrum. Seminal recep- 

 tacle consists of two chambers. Their walls calcareous, sometimes 

 membranaceous. No appendage to the spermatophore. Vas deferens 

 long, slender and coiled several times. Shell generally covered 

 with setae, rarely naked. 



C. Dorsal median kiel of the carapace present, but rather 

 faint. No tooth at the anterior, inferior angle of the carapace. 



a. First to third pairs of pereiopoda unispinose. In males 

 the fourth joint of the fifth pair of pereiopoda has a 

 tubercle, the pleuron of the first pleonic segment is 

 notched at the inferior margin and the sixth pair of ple- 

 opoda has also a tubercle. Exterior as well as the interior 

 walls of the seminal receptacle are calcified. Its cavity is 

 divided by a median septum and opens by two slits. Tail 

 segment unarmed. 



'& 



5. In females the first joint of the fourth pair of per- 

 eiopoda expands to a disc-like process which abuts 

 just the anterior margin of the thelycum. Lateral 

 plates of the thelycum is flat for the most part. Dis- 

 tal end of the inner lamina of the petasma is a flat 

 process. Distal end of the outer lamina extends 

 laterally. Rostrum serrated to its apex, 8 or 9 

 dentate. First — fourth segments of the pleon naked. 



P. affinis. 



6. In females the first joint of the fourth pair of 



