56 



only a little in advance of the outer terminal spines. The e.xopod of the uropods is in the 

 male (fig. 7 a) a little more narrow than in L. typus, about six times as long as broad, and 

 the marginal process is frequently still more produced (fig. jd) than in L. fypus. In the female 

 the exopod is a little or somewhat more than five times as long as broad ; its end is sometimes 

 shaped as in L. tvpiis, sometimes the terminal margin is considerably oblique (fig. 7^), and 

 then the marginal spine reaches almost or fully as far backwards as the upper distal angle. 



The petasma (fig. 7^) has the terminal portion thicker than in L. typiis, and it terminates 

 in three triangular lobes. Fig. 7/, drawn with transmitted light, exhibits these lobes, the fine 

 transverse lines {s.) on the two largest lobes, furthermore the enclosed processus ventralis {pv.). 

 In fig. jg the sheath is seen from another side, open, and the processus ventralis is turned 

 totally out and bent backward ; this rather broad, lamellar process differs considerably from 

 that in L. typus in having the terminal incision much deeper and narrowing to its acute end; 

 the long hook-shaped process found in L. typus is entirely wanting. The process at the front 

 margin of the pleopod beyond the insertion of the petasma is nearly as in L. typtcs, but with 

 .some more prickles on its end. 



Length of good-sized specimens of both sexes i [.5 mm. 



Distribution. — The list of the localities shows that L. orientalis has been taken 

 at more than twenty stations; it is thus much more common in the "Siboga" area than Z. typus, 

 but in most cases the number of specimens is small. The Copenhagen Museum possesses L. 

 orientalis from two places, viz. Manilla ("Galathea") and Aden (Mr. H. Mortensen); the last- 

 named locality, at the entrance to the Red Sea, is of interest. 



Group B. 



The animals belonging to this section differ in aspect very considerably from those of 

 group A by the proportionately short eye-stalks (PI. IV, fig. 8; PL V, figs. 2a, 3«, /\.a). These 

 are sometimes rather slender to somewhat from the eyes, but most frequently they are moder- 

 ately or decidedly inverted conical ; the eyes are smaller in proportion to the animal than in 

 group A, and only slightly or not at all larger in the males than in the females. The exopod 

 of the uropods differs in breadth according to species and sex, from slightly more than five to 

 only four times as long as broad. 



The group comprises 4 species. The females of two of the species, L. Faxoiii and L. 

 Hanseni, can be separated from one another and from the two other species, L. ititermedius 

 and L. penicillifcr ^ but it is sometimes impossible to separate with certainty females of the 

 two last-named species. — The following keys may be useful for students of the genus. 



Key to the Males. 



a. Terminal portion of the petasma has the end broadly rounded, a 

 number of fine transverse lines on the inner side of its distal part, 

 and two freely protruding, very conspicuous, small plates at the front 

 margin. Proc. ventralis is a narrow plate with its broader terminal 



