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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 longicornts 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. 
Its length is rather less 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 4o, 
off Pulu Kawassang, Paternoster Islands. 
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