132 



Heterorliabdus papilliger Cleve, 1903, p. 363. 

 Heterorhabdus papilliger Cleve, 1904, p. 191. 

 Heterorliabdus papilliger Wolfenden, 1905 (a), p. 1012. 

 Heterorhabdus papilliger Sars, i905(/>), p. 3. 

 Heterorliabdus papilliger Esterly, 1905, p. 184, fig. 38. 

 Heterorliabdus 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). 



Heterorhabdus papilliger has a close resemblance to Heterorliabdus e/at/si 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, i905(/>). 



This genus was established by Sars in 1905 for the reception of a Calanoid closely related 

 to Heterorhabdus and Dissela. 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 truneatus 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 XXXIX, fig. 1 2). 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 

 margfin to the base of the grenital segment. The g/enital segment when viewed from above 

 appears almost rectangular in outline. It is nearly as broad as long. lts 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 



