ON A SPECIES OF A CET ES FROM JAPAN. 



165 



each of which shows a pair of very long ciliated hairs. Each articulus of 

 the distal portion has a pair of long ciliated hairs on the outer margin, 

 while its inner margin is provided with short hairs in some articuli. Some 

 articuli in the proximal as well as the distal portion of the flagellimi 

 have the distal margin serrated. These serrated articuli are distributed at 

 irregular intervals. 



A species of Sergestcs, caught in abundance during winter in the Bay 

 of Suruga, has also the flagellimi of the second antennae similarly bent and 

 divided into the two portions. Thus, I am inclined to think that this 

 peculiar bending of the said flagellimi is probably characteristic to the 

 family Sergeatidse. 



The mandibles are furnished with the synaphipod, long and two-jointed. 



The second pair of maxillipeds is stout, flattened, and a little longer 

 than the first pereiopoda. 



The third pair of maxillipeds is stout and long, being longer than 

 the first and second pereiopoda. 



There are only three pairs of pereiopods. These are all chelate. 

 As in many other forms of the Sergestidae, both the propodos and carpos 

 of the first pair of pereiopoda have each a group of serrate hairs, which aid 

 in their function as a prehensile organ. The fourth pair of pereiopoda is 

 entirely wanting. In the male, there is a pair of protuberances behind the 

 third pair of pereiopoda. These are the abortive fifth pair of pereiopoda ; the 

 reproductive glands open on the inner side of the protuberances. The 

 thoracic somite with the fourth pair of pereiopoda is very short, and its 

 pair of ganglia is very closely situated to that of the preceding somite. 

 The somite with the fifth pair of pereiopoda is very long. 



In the female, the coxal joint of the third pereiopoda is wide, and the 

 oviducts open on the sternum by a pair of small transverse slits, situated 

 very close to the root of the appendages. On the ventral side of the 

 somite with the fourth pereiopoda, there is a roof-like, notched protu- 

 berance turned backwards. This roof, together with a little cavity 

 beneath it, may probably represent the thelycum. 



The five anterior somites of the pleon are subequal in length. The 



