21 



September. 



Inhabits the shallow sandy bottom, not deeper than 20 metres. 

 In autumn this species is found to form large shoals and migrates in 

 a bay. 



Is distributed in the Pacific coast of our country from the Tokyo 

 Bay to Kushu. 



Feeds chiefly on microscopical algae. 



This species is one of the very important prawns. It is known 

 under the names of "shibayebi," "ohzoyebi," etc. 



PENAEUS INTERMEDIN w s P ec. 



The shell with shallow, irregular and setae-grown grooves. The 

 rostrum is straight, 9 dentate, toothed to the apex and is equal in 

 length to the peduncle of the first pair of antennae. Continuous to 



the rostrum, there is a low kiel runnino- to the hind margin of the 

 carapace. The first pair of pereiopoda bispinose, the second and third 

 pairs unispinose. The first joint of the fourth pereiopoda is expanded 

 and meets the lateral sides of the central plate of the thelycum. The 

 tail segment is grooved and is armed with three pairs of long movable 

 spines. 



The thelycum is much like the same organ of P. incisipcs, but the 

 external ridge of the lateral plate is low and inconspicuous. The cavity 

 of the seminal receptacle is divided into two by a median septum. 



Only two female specimens are known from the province of Tosa. 



