13 



found at each basisal joint of the first and second pairs of pereiopoda. 

 Three small movable spines are found on each side of the telson. 



The lateral plates of the thelycum come in contact with each other 

 at the median line (PL VII, 2 A). The median plate is small and is 

 partly covered by the lateral plates. At the anterior part of the 

 median plate, there is a protuberance which is divided into two thin, 

 calcareous horns. The cavity of the seminal receptacle is single and 

 its wall is membranaceous. 



The petasma is simple (PL VII, 2). Its outer margin is very 

 thin and the distal end of the inner lamina ends promptly. The ap- 

 pendage of the spermatophore is soft and band-shaped, does not pro- 

 trude out of the seminal receptacle. Probably it does protrude at first, 

 but it would be worn away soon. 



The color is light brown or sometimes greyish, especially in young 

 animals. The dorsal median kiel of the carapace and the same in the 

 fourth to the last pleonic segments are black. There are also some 

 dark marks near the ventral margin of the pleonic segments. 



The langest specimen in my collection measures 15 cm. in length. 



This is rather a rare species. Specimens in our laboratory are 

 from the Tokyo Bay and Kagoshima. 



This is very closely allied to P. canaliiidatus ; but is easily dis- 

 tinguished from it by the shorter rostrum, broader grooves, the lon- 

 gitudinal opening of the seminal receptacle, the appendage of the 

 spermatophore, etc. Also very closely allied to P. caranvote; but the 

 latter has a spine on the coxal segment of the first to third pairs of 

 pereiopoda and the spermatophore has a soft wing-shaped appendage, 

 which protrude out of the seminal receptacle. 



As this animal is very few in number, it is confounded with other 

 species and has no special name for itself. 



