54 



of the uropods differs as usual in the two sexes. In the male (figs. 6 a — 6 c) it is from a little 

 more than five to more than five and a half times as long as broad, and the apical marginal 

 process is moderately long or very long, but the terminal part of the uropod shows yet con- 

 siderable individual variation, as sometimes the end of the uropod has its margin somewhat 

 flatly curved, which is the case when the marginal process exhibits itself nearly as a continuation 

 of the uropod, while sometimes the end of the uropod has the margin deeply curved, and in 

 this case the process originates a little before the terminal upper angle of the uropod: forms 

 intermediate between the two shapes described are common. In the female the exopod is five 

 times as long as broad; its end (fig. 6d) is oblique so that the marginal spine, w^hich is smaller 

 than in the males, originates slightly or somewhat before the upper terminal angle of the uropod, 

 and reaches to or a little beyond that angle. 



The petasma is shown in fig. 6^ from the inner side and partly unfolded, so that its 

 terminal portion is removed from the pleopod. This terminal portion is seen to be proportionately 

 robust as compared with its shape in the forms figured on PI. V; in fig. 6/i it is shown with 

 transmitted light, and the shading is made according to the degree of chitinization. The end is 

 broad, flatly and obliquely rounded with a rudimentary protuberance; the long hook {/i) is very 

 conspicuous, and the lamelliform processus ventralis {/>v.) rather distinct. Fig. 6i exhibits the 

 same portion, but the proc. ventralis has been removed. The transverse, undulating, fine, dark 

 lines are distinct on both figures. Fig. 6k exhibits the terminal portion of a third specimen; 

 the lamelliform proc. ventralis is turned out of the sheath ; a special description of this process 

 is scarcely needed, and only one thing may be emphasized, viz. that the bottom of the deep 

 terminal incision is transverse. The process at the front margin of the pleopod beyond the 

 insertion of the petasma is seen (fig. 64'') to be slender, much longer than thick, with two or 

 three sometimes nearly indistinct prickles on the rounded end. 



Length of a large male (from the tropical Atlantic) 12.4 mm., of a large female 12 mm. 



Distribution. — L. iypus is evidently far from common in the "Siboga" area, as it 

 was taken only at four places, and three among these are even rather near each other. The 

 Copenhagen Museum possesses it from Manilla ("Galathea"); from lat. i6°8'S., long. iii°5o'E. 

 (Capt. Andrea), and from the Bay of Bengal ("Galathea"); furthermore from more than thirty 

 localities in the Atlantic, and from Messina. Of the Atlantic places more than twenty five are 

 north of the line, the most northern at lat. 34° 10' N., long. 42°io'W. ; the two most southern 

 localities are respectively lat. 28°43'.S., long. 25°i4'W., and lat. 40°32'S., long. 52°2'W. 

 As our Museum possesses such a rich material from so many places in the Atlantic, and I 

 did not find a single male specimen of the other species with long eyerstalks among the 

 material from this Ocean, I think that all specimens referred to L. reynaudi M.-Edw. (Z. acestra 

 Dana) by Ortmann (1893) and taken by the German Plankton-Expedition belong to L. typus. 

 Ortmann says that it is "eine echte Plankton-Form, die sich nur in den warmeren Meeren 

 findet, dort aber so allgemein verbreitet ist, dass sie fast in alien Fangen erhalten wurde"; he 

 enumerates an enormous number of stations where it has been gathered, and his Taf. X, a 

 track-chart of the expedition, shows its quantitative occurrence; the most northern of the stations 

 is in the Florida current far south of New Foundland about at lat. 42° N. 



