1 6 



The animal generally attains the length of 15 — 20 cm. 



This is a rather rare species. I have collected it from the Tokyo 

 Bay and Bay of Ise. 



Is known under the names of "ushiyebi" or " kurokumayebi." 



This species is very intimately allied to P. ashiaka, so that these 

 two species are often confounded together. The length of the flagel- 

 lae of the first antennae, length of the rostrum, petasma, color, etc. 

 distinguish these two species. 



PENAEUS AFFINIS. 



(PI. IV, 1) 



Pcnacus affinis, M-Edw., Hist. Nat. Crust (1837); Sp. Bate, Ann. 

 Mag. Nat. Hist. 5 series viii, pp. 179 — iSo, PI. XII, fig. 6 (1S81). 



Penaeus monoccros, Ortmann, Zool. Jahrbuch. Abth. Syst. p. 450 

 (1890). 



The shell for the most part smooth and thick. The carapace and 

 the pleonic segments posterior to the fourth segment have more or less 

 small, irregular grooves in which minute setae are growing. The 

 rostrum nearly straight, but in the female it is a little elevated at the 

 anterior end. It is 8 or 9 dentate, toothed to its tip. There is a 

 faint kiel at the median longitudinal line of the carapace and also bet- 

 ween the hepatic tooth and the posterior margin of the carapace. 

 The second joint of the first three pairs of pereiopoda is respectively 

 armed with a spine. Males have a blunt tooth on the fourth joint of 

 the fifth pair of pereiopoda. On the peduncle of pleopoda, there is a 

 shallowd groove, occupying about 1/5 of the breadth of the external 

 side of the peduncle. In such a groove, we find short setae. In 

 males the sixth pair of pleopoda has a tubercle on the peduncle. The 

 telson has many, shallow, longitudinal grooves, grown with setae. 



The central plate of the thelycum (PI. VII, 5 A) is low and small, 



