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10. Family PsrupopIAPTOMIDAE. 
Genus Pseudodiaptomus Herrick, 1884. 
The members of this genus, established by Herrick in 1884, are readily recognised by 
the structure of the fifth pair of feet of the two sexes. The fifth pair of the female consists 
of a two-jointed basiopodite and an exopodite composed of two or three joints. The endopodite 
is stated to be entirely absent, but one of the species found in the plankton collected by the 
‘Siboga’, shews an indication of what appears to.be a very rudimentary endopodite. The male 
fifth pair forms a prehensile appendage. The basiopodite is two-jointed. The exopodite of the 
right side is composed of two or three joints. The last joint is usually claw-like. The exopodite 
of the left side consists usually of two joints. The last joint is frequently lamelliform. ; 
Two species were represented in the plankton collected by the ‘Siboga’. 
1. Pseudodiaptomus aurivillic Cleve. 
Pseudodiaptomus auriilli Cleve, rgot, p. 48, pls. VI & VII. 
_ Pseudodiaptomus aurivilliz Thompson & Scott, 1903, p. 248, pl. II, figs. 24—26. 
This species although very limited in its distribution, proved to be rather plentiful in 
one of the gatherings. It was present at the following stations. 
Stat. 16, 4 specimens. — Stat. 71, 6 specimens. — Stat. 133, 3 specimens. — Stat. 174, 8 
specimens. — Stat. 213, 96 specimens. 
Pseudodiaptomus aurtvillit is easily separated from the other members of the genus, 
by the characters of the fifth pair of feet of the two sexes. The second joint of the exopodite 
of the female fifth pair is very small. It terminates in a moderately long spiniform claw. The 
right foot only of the male is furnished with an endopodite. The second joint of the basiopodite, 
and the first joint of the exopodite of the right foot have each a strong outer edge spine. 
CLEVE obtained the type specimens from plankton collected in the Malay Archipelago. 
It has also been recorded, and partly illustrated from specimens found in the collections taken 
by Professor HeERpMAN, during his investigations on the pearl banks in the Gulf of Manaar, Ceylon. 
2. Pseudodiaptomus clevet nov. sp. Plate XXXVI, figs. 1—8. 
Female — length 1,75 mm. j 
Seen from above, the female bears a general resemblance to Pseudodiaptomus aurivilliz. 
The last thoracic segment is produced into strong spines. Two dorsal spines are also present 
on the surface of the last thoracic segment, just in front of the junction with the abdomen. 
Viewed from the side, the forehead appears evenly rounded. The last thoracic segment is 
rather narrowly rounded at the posterior end, and the dorsal Soe AVES, quite visible (Plate 
DOOR tea) 
The abdomen is composed of four ségments. The combined length of the Avdomen and 
furca is contained one and a half times in the total length of the cephalothorax, from the 
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