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One female apparently belonging to the above species was obtained from the plankton 

 collected at each of the following two stations. 

 Stat. 66. — Stat. 121. 



Length — 2,8 mm. 



The antennules are two-jointed and are equal to two-thirds of the length of the cephalic 

 segment. The abdomen is composed of three segments. The genital segment is sub-quadrangular 

 in shape and is equal to nearly twice the combined length of the next two segments. It is 

 considerably shorter than the united length of the next two segments and furcal joints. The 

 segment is marked by a well defined suture traversing the middle. The third segment is very 

 short and is only equal to about half the length of the second segment. The furcal joints are 

 four times longer than the anal segment. Each joint is furnished with one outer marginal seta 

 and four apical setae. The second inner seta is shorter than the others (Plate LVII, fig. 3). 



The fifth pair of feet is sub-cylindrical in shape with a distinct contraction in the middle. 

 Each foot is furnished with one inner marginal seta and two apical setae (Plate LVII, fig. 4). 



The long antennules with their rather pointed ends, and the shape of the fifth pair appear 

 to be very characteristic features of this species. The only difference between the 'Siboga' 

 specimens and the illustrations given by Giesbrecht and by my father, is the absence of a 

 third seta on the apex of the fifth pair of feet. 



Monstrilla longicornis has been recorded from the British Coasts and from the Mediterranean. 



3. Monstrilla orcula nov. sp. Plate LVII, figs. 5 and 6. 



Female — length 3,8 mm. 



Seen from above, the body appears moderately slender. The cephalic segment is greatly 

 contracted in front and is slightly narrowed behind. It is slightly longer than the posterior part 

 of the animal. The frontal margin is concave. 



The abdomen is composed of three segments. The genital segment is sub-cylindrical in 

 shape with a distinct constriction at the middle where it is traversed by a well defined suture. 

 lts length is rather Iess than twice the combined length of the next two segments. It is shorter 

 than the united length of the next two segments and furcal joints. The second and third 

 segments are of about equal length. The furcal joints are nearly equal to twice the length of 

 the anal segment. Each joint is furnished with one marginal seta and five apical setae. The 

 middle apical seta is distinctly shorter than the others (Plate LVII, fig. 5). 



The fifth pair of feet is moderately large and is distinctly bi-lobed. The inner lobe is 

 narrower than the outer one and extends beyond the end of it. The apex of the inner lobe 

 is furnished with two setae. The outer lobe is short and stout. The apex is furnished with 

 three setae (Plate LVII, fig. 6). 



This species can readily be separated from the other members of the genus by the 

 bi-lobed structure of the fifth pair of feet, and by the inner lobe extending beyond the apex 

 of the outer lobe. 



Occurrence. - - One female was obtained from the plankton collected at Station 40, 

 off Pulu Kawassang, Paternoster Islands. 



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