638 



PROCEEDINGS OF THE NATIONAL MUSEUM. 



VOL. 41. 



Fig. 46. — Diastylis 

 bidentata, imma- 

 tuee female, an- 

 terior part of 

 body from above. 



a distance much greater than the length of the ocular lobe. The 

 ocular lobe is slightly broader than long and bears a few small denti- 

 cles; just behind it, on the frontal lobe, are two short transverse 

 denticulated ridges. 



The pleural plates of the second free thoracic somite are pointed 

 anteriorly and almost or entirely conceal those of the first somite. 

 The dorsal part of the fourtli somite is strongly 

 produced backwards in the middle line. 



The telson is longer by about one-half than the last 

 somite and longer than the peduncles of the uropods; 

 it is shghtly expanded at the base and then contracts 

 rapidly to a narrow distal part; the post-anal division 

 is 1^ times as long as the pre-anal. There are about 

 10 pairs of lateral spines and a pair of somewhat 

 larger apical spines. 



Peduncle of antennule with last segment slender, 

 nearly half as long again as the second, first shorter 

 than second and third together. Penultimate seg- 

 ment of antenna elongated. 



Third maxilUped not expanded distally; its length 

 along the inner edge nearly eight times its greatest 

 width; merus expanded externally, broader than iscliium. 



The first pair of legs have the basis about one-tliird longer than 

 the distal segments together, with some small 

 teeth on the lower surface and inner edge ; the last 

 three segments are subequal. In the legs of the 

 second pair the carpus is only a Uttle longer than 

 the last two segments together. The legs of the 

 tliird and fourth pairs have each a minute exopod 

 of two segments. 



The peduncle of the uropods is spinous on the 

 iimer edge. The endopod is about three-fourths 

 as long as the peduncle and very slightly longer 

 than the exopod; its three segments are well 

 defined, the first only a little less than twice as 

 long as the other two together. The inner edges 

 of both rami are spined. The terminal spine of 

 the endopod is short, well defined at the base; 

 the exopod has two apical spines, one of them long and slender. 

 Adult male. — Total length, 12mm. 



Differing from the female in the usual characters, the body being 

 more slender and the carapace less arched. The ridges of the cara- 

 pace are strongly marked and arranged as in the female, but the 

 tooth of the second ridge is represented only by a shglit angulation 

 of the ridge not projecting from the surface, and the transverse 



Fig. 47.— Diastylis bi- 

 dentata, immature 

 female, first leg. 



