ra Duchassaii tti, Coralliaires « U -, Antilles, iS6o, p. 25. 



1 K^llikcr. Iconcs I listo , p. I 38. 



PU Wright and Studer. (. 'hallen irts, the Alcyonaria, [889, p. 1^7. 



. homson and Hcnderson. Pearl Oystei Fisheries Rcports, the Alcyonaria, 1905, p. 304. 



rhe original describer, Lamouroux, gave a definition for this genus that needs little 

 change to fit it for modern use. h is as follows: 



'Polypier dendroïde, rameux, souvent dichotome; ramaux cylindriques et roides; .1 

 '■inent comprimé; . dans l'étal de dessication, subéreuse, ou terreuse, très-épaisse, 



int peu d'eflfervescence avec les acides, et couverte de cellules éparses, grandes, nombreuses, 

 /ent in< I qui ne sont jamais saillantes". 



Eliminating non essential points, the difinition used for the present work will be as follows: 

 enenchyma thick, calyces included and distributed on all sides of the stem and branches. 

 Spicules in the form of warty spindles and clubs, usually in two layers. Axis enrirely horny, 

 at the base of the stem of large specimens. 



The character of the axis will ditïerentiate this genus trom Plexaurella, which greatly 

 it superficially, and from Euplexaura and Pseudoplexaura. The characters of the 

 spicules will separate it from Plexauroides and Hicksonella. 



The type of this genus is Plexaura heteropora (Lamarck). 



( >wing to the superficial resemblance between Plexaura and Plexaurella, both genera 

 abundant in species, it is impracticable, without recourse to the types, to teil which of the 

 species originally described should be placed in Plexaura. Both of these genera are but sparsely 

 represented in previous collections from the Western Pacific, or Indo-Pacific region. Hence it is 

 not surprising that the species in the Siboga collection are all apparently new. 



1. Plexaura aggregata new species. (Plate I, figs. 1, ia; Plate IV, fig. 1). 



58. Anchorage off Seba, Savu Island. Up to 27 meters. 

 Stat. 65*. 7 o' S., 120 34.5 E. Flores Sea. Depth changing rapidly from 400 — 120 meters. 



( <>ral bottom. 

 Stat. 213. Saleyer anchorage, and surroundings. Up to 36 meters. 

 Stat. 258. Tual anchorage, Kei [slands. Reef. 22 meters. 

 Stat. 515. Anchorage Ka-t ■ >! Saihis Besar, Paternoster Islands. Up to 36 meters. 



Colony consisting of a dense clump of branches, 36 cm. in height. The branches all 



spring from the base <>l the colony and al most immediately begin to subdivide. The base is 



about 4.5 cm. broad, and the largesl branches have a diameter of about 2 cm. The branches 



divide irregularly, but ordinarily the division is not dichotomous, until ultimate branchings of 



■ r io lh order are attained, the result being hundreds of terminal twigs with a diameter 



mm. All of the branches are round and smooth, and distinctly enlarged at their 



ends. 'I he calyces are inserted on all sides of the branches, and are evenly spaced, averaeiiiL; 



•ut 1 mm. apart. TIn- ccenenchyma is very thick. 



The individual calyces are completely inserted. leaving the surface of the branch perfectly 



re pitted by the calyx apertures. These pits are quite small, in alcoholic 



pits being oval instead of round, their greater diameter being parallel to the 



