366 arcturidj:. 



This species is more robust than either of the two 

 following ; it is also more strongly tuberculated, the 

 tubercles extending over the two segments preceding the 

 long one, which is somewhat transversely furrowed. 

 The head and terminal segments of the body are rather 

 broader in the male, but of an equal breadth throughout 

 in the opposite sex ; the females are twice the size of 

 their partners, and of a whitish colour ; the terminal 

 portions of the body are generally directed upwards. 

 The head is almost square, with the eyes prominent and 

 nearly circular : the anterior angles of the head are 

 produced in front of the eyes, forming a deep frontal 

 emargination, in which the anterior (upper) antennas are 

 inserted; these are not longer than the head, and have the 

 basal joint large, the next row short, and the flagellum 

 long, cylindric, and terminated by setae. The lower 

 antennae are nearly as long as the body, and very robust; 

 the first joint is very short, the second rather longer, with 

 a deep external notch, the third about as long as the 

 head ; the two next are very long, each being about one- 

 fourth of the whole length of the body ; the flagellum 

 is very short and finely serrated beneath, each being 

 gradually smaller, the last terminated by a minute acute 

 point ; the antennae are usually carried in a downward 

 direction. The parts of the mouth are very minute and 

 delicate. The lip is transverse, rounded at the sides and 

 emarginate in front. The mandibles are small, horny, 

 broad, and armed with several teeth, without any palpi- 

 form appendage. The interior pair of maxillcB are very 

 thin, transparent, and deeply ciliated. The second pair 

 of these organs are larger, with a terminal lobe and a large 

 external sub articulated appendage, the last division of 

 which is much larger than the rest, curved and ciliated 

 at the tip. 



