654 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.41. 



DIASTYLIS SULCATA, new species. 



Female (with developing oostegites). — Total length, 13 mm. 



Carapace elongated and slender, its height a little less, and its 

 transverse width a little more, than one-half of its length. The 

 dorsal edge, as seen from the side, is only very shghtly arched. A 

 transverse ridge crosses the dorsal surface just behind the ocular 

 lobe, where it is very prominent and bears about six strong teeth; 

 passing downward and slightly backward on each side, it is less 

 strongly marked but becomes more prominent again as it curves 

 sharply backward to run parallel to and a little distance above the 

 lower edge of the carapace, from which it is separated by a deep 

 groove; it dies out before reacliing the liind margin of the carapace; 

 along the lower part of its course it is obscurely dentated. The 

 pseudorostrum is horizontal and acute; there is no distinct antennal 

 notch, but the anterior part of the lower edge of the carapace is 

 rather coarsely serrate. The ocular lobe is very small and there is 

 no distinct eye. 



Fig. 76.— Diastylis sulcata, immature female, from the side. 



The free thoracic somites together are shorter than the carapace; 

 the pleural plates of the second somite are narrowly rounded in front 

 and overlap, but do not conceal those of the first; the lateral expan- 

 sions of the third and fourth somites are more strongly produced 

 backward than they are in D. rathTcii, that of the third somite being 

 about one-tliird as long as the carapace ; the last thoracic somite is 

 produced postero-laterally in a pair of stout spiniform teeth. 



The abdomen, mcluding the telson, is distinctly longer than the 

 cephalothoracic region. The fifth somite is slightly longer than the 

 sixth. The telson is longer by about one- third than the sixth somite, 

 narrowing almost from the base, the post-anal portion twice as long 

 as the pre-anal, with about nine pairs of short lateral spinules and 

 a pair of short apical spinules. 



The peduncle of the antennules has the first segment nearly three 

 times as long as the second and twice as long as the third. The seg- 

 ments of the antenna are short. 



The first legs have the basis nearly half as long again as the distal 

 segments together; the last three segments are subequal. The sec- 



