8 mm. in height and 1.3 mm. in diameter at the base. They are closely approximated on the 

 distal parts of the colony and more distant, although still rather closely emplanted on the 

 proximal parts. The margin is surrounded by 8 lobes which form an 8-rayed figure when 

 viewed from above. The calyx walls are filled with densely tuberculate spindles which are 

 usually horizontal on basal parts and tend to be vertical on distal parts, especially in the mar- 

 ginal lobes. In the ccenenchyma the spicules are longitudinal as a rule. The polyps are com- 

 pletely retractile, and in retraction lie well below the infolded lobes of the calyx margin. The 

 collaret is very weak, scarcely evident. The tentacles are covered on their dorsal surfaces by 

 small tuberculate spindles which are longitudinal on the distal parts and tend to an en chevron 

 arrangement on the proximal parts. 



The ccenenchyma is moderately thin. A cross section of the stem shows inconspicuous 

 water-vascular canals and a corneous axis which is slightly flattened. 



Spicules. Stout, densely tuberculate spindles of moderate size, with the tubercles not 

 arranged in distinct whorls, are the characteristic form of this species. Those in the tentacles 

 are smaller and more slender. Rarely a clubshaped form is seen. 



Color. The colony, in alcohol, is a light brown with a faint reddish cast in places. 



Genus Platycaulus Wright and Studer. 

 Platycauhis Wright and Studer. Challenger Reports, the Alcyonaria, 1889, p. 148. 



The original definition of this genus is as follows : 



"Colony branched, the branches in one plane, anastomosing. The axis is horny, flattened, 

 with a calcareous centre and calcareous particles interspersed amid the horny layers : the nutrient 

 canals surrounding the central axis almost as in Plexaiira. Polyps prominent, on the sides of 

 the stem and branches, retractile within Verrucae. Ccenenchyma moderate, like shagreen. Spicules 

 straight and curved spiny spindles and stellate forms". 



The type, and hitherto the only known species of the genus Platycaiilics is Platycauhts 

 danielsscni Wright and .Studer. 



I. Platycaiilus siboga: new species. (Plate II, figs. 2, 2«; Plate III, fig. 4). 



Stat. 213. Saleyer Anchorage and surroundings. Up to ^6 meters. 



Colony flabellate, not reticulate, although there are a few anastomoses, loose and flabby 

 in texture, 35 cm. high. -Several upright stems spring from a single encrusting base. The largest 

 of these has its main stem and many of the branches and twigs flattened. The stem forks 

 2 cm. from its base into two unequal branches the largest of which is 6.5 mm. X 5 mm. in 

 section. After giving oft" several small lateral branches it again forks, 1 1 cm. from its base, 

 and the resultant branchlets again give off irregularly disposed lateral branchlets at intervals 

 of about I cm. Branches of the 6'*^ order are sometimes attained. In a few cases the branches 

 anastomose, but not often. The ultimate twigs are flattened, being about 2 mm. by i mm. in 

 section, short, and generaly pinnate in arrangement. The calyces are usually lateral in position, 



