2 ARKIV FÖR ZOOLOGI. BAND 14. N:0 10. 



Japan, May 28, 1914. Depth: 2—3 m. The large size of 

 this specimen and its excellent preservation more than com- 

 pensate for the lack of duplicates. 



Specific characters of female. Carapace obovate, one- 

 third longer than vvide, considerably narrowed anteriorly, 

 widest through the fourth thorax segment, and entirely con- 

 cealing the swimming legs. Posterior sinus narrow, one-half 

 the length of the carapace, evenly rounded at the base, with 

 nearly parallel sides. Cephalic area in the form of a spheri- 

 cal triangle, the anterior shorter side close to the frontal 

 margin of the carapace. 



The longitudinal chitin rods are well-defined and rather 

 strongly curved, but neither the dorsal brain nor the eyes 

 are visible. 



From either side of the cephalic area near its posterior 

 end a groove runs diagonally outward and forward toward 

 the margin of the carapace. 



From about the center of this groove a longitudinal 

 branch runs backward along the center of each lateral lobe 

 nearly to the posterior end. 



The respiratory areas in the lateral lobes are near the 

 anterior ends; the front area is elliptical in outline, a little 

 smaller than the sucking disk, and partially concealed by 

 the latter. The posterior one is separated by a considerable 

 interval from the anterior one and is club-shaped, its post- 

 erior end being somewhat enlarged. 



The abdomen is elliptical, as wide as long; the posterior 

 sinus is slitlike, less than one-third the length of the ab- 

 domen, and the anal laminae are basal. The first antennae 

 have strong hooks on the anterior and lateral margins, and 

 a stout spine on the posterior margin. 



Each second antenna has two spines at its base, the 

 outer one considerably smaller than the inner; there is also 

 another larger spine on the ventral surface of the head, be- 

 hind the base of each antenna. 



The sucking disks are placed far forward, just behind 

 the lateral sinuses; each is about one-sixth the greatest 

 width of the carapace, or a little less than one-third the 

 width at the level of the disks themselves. The supporting 

 ribs of the margins of these disks are very complicated, as 



