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Heterorhabdus papilliger Cleve, 1903, p. 363. 
Fleterorhabdus papilliger Cleve, 1904, p. 191. 
Heterorhabdus papilliger Wolfenden, 1905 (a), p. 1012. 
Heterorhabdus papilliger Sars, 1905 (6), p. 3. 
Fleterorhabdus papilliger Esterly, 1905, p. 184, fig. 38. 
FHleterorhabdus papilliger van Breemen, 1908, p. 120, fig. 138. 
One female identical with the above species was obtained from the plankton collected 
at each of the three following stations. 
Stat. 128 (HENSEN vertical net, 700 metres to surface). — Stat. 216. — Stat. 276 (HENSEN © 
vertical net, 750 metres to surface). 
Fleterorhabdus papilliger has a close resemblance to Heterorhabdus claust but it can be 
separated from that species by the much shorter antennules. The antennules scarcely reach to 
the end of the furcal joints. Other differences can be detected on comparing the various 
appendages of the two species. 
This species appears to have a moderately wide distribution. It has been recorded from 
the tropical and colder areas of the great oceans by various observers. 
Genus Mesorhabdus G. O. Sars, 1905 (0). 
This genus was established by Sars in 1905 for the reception of a Calanoid closely related 
to Heterorhabdus and Disseta. It is separated from these genera, by the great development of the 
spines on the two apical lobes of the first maxillipedes. The furcal joints are quite symmetrical. 
One species, apparently undescribed, was represented in the plankton collected by 
the ‘Siboga’. 
1. Mesorhabdus truncatus nov. sp. Plate XXXIX, figs. 12—21. 
Female — length 7 mm. 
Seen from above, the body appears robust and irregularly oval. The greatest width is 
in the middle of the first thoracic segment. The frontal margin of the cephalic segment is 
boldly rounded. The rostral papilla is very slightly indicated in the middle of the frontal curve. 
The distal end of the last thoracic segment is moderately wide. It is almost truncate. The lateral 
margins are slightly extended into very small projections (Plate XX XIX, fig. 12). Viewed from 
the side, the distal end of the last thoracic segment is broadly rounded, then slightly emarginate 
as it joins the dorsal line. The rostral filaments are long and slender (Plate XXXIX, fig. 14). 
The abdomen is composed of four segments. The combined length of the abdomen and 
furca is contained nearly three times in the total length of the cephalothorax, from the frontal 
margin to the base of the genital segment. The genital segment when viewed from above 
appears almost rectangular in outline. It is nearly as broad as long. Its length is slightly less 
than the combined length of the next three segments. The ventral surface is considerably 
inflated, and is produced in the middle into a blunt pointed process. The second, third and 
fourth segments are comparatively short. They are of nearly equal length. The furcal joints 
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