SYNOPTICAL KEY TO THE JAPANESE SPECIES 



OF PENAEUS. 



I. Lower margin of the rostrum toothed, the cavity of the seminal 

 receptacle single and its internal wall membranaceous. Shell smooth, 

 having no setae. Spermatophore has an appendage. Vas deferens 

 short and thick, not much convoluted. 



A. Only one tooth on the inferior margin of the rostrum. 

 Three small spines on each side of the tail segment. Dorsal 

 median line of the carapace is grooved. Grooves running on 

 each side of the central groove reach the posterior end of 

 the carapace. Pereiopoda stout. The posterior end of the 

 inner lamina of the petasma is prolonged and is turned ex- 

 teriorly. Second segment of the first and second pairs of 

 pereiopoda ha w a spine. 



i. Dorsal median groove of the carapace is nearly equal 

 in breadth to the lateral grooves. Lateral plates of the 

 thelycum is not divided and the opening of the seminal 

 receptacle has the shape of a lateral slit. Spermatophore 

 has a wing-shaped appendage. External rim of the pet- 

 asma thick. Anterior end of the inner lamina of the 

 petasma ends with a soft crooked protuberance. Rostrum 

 8 — 10 dentate above. 



P. canaliarfatits. 



