338 DE. S. J. HICKSON — EEVI8I0N OF TKE 



Stereosoma the horny substance that is formed lies inside the ectoderm, whereas iu 

 Cornularia it is outside it. 



The mesenteries present well-marked muscle-ridges and muscular bands. The 

 muscles are used for producing the graceful swaying and bending movements that I 

 noticed in the living condition. 



There is a small and not very well-defined siphonoglyphe (Plate L. fig. 2), and the 

 walls of the stomodaeum in preserved specimens are slightly folded. 



There are no spicules in the body-walls, tentacles, or stolon. 



The stolon is a moderately thick plate-like structure containing numerous ramifying 

 canals. 



The tentacles are long and delicate, and present the remarkable feature of possessing 

 only a few small teat-like pinnae, separated from one another by considerable intervals- 

 In this feature Stereosoma presents a character that seems to separate it from all the 

 other Stolonifera. In all the species of Clavularia that I have examined the pinnae 

 are exceedingly numerous and very closely set, so that the tentacle has a considerable 

 resemblance to the vexillum of a feather. The tentacle of Stereosoma has no resem- 

 blance whatever to a feather. 



The elongated slit-shape mouth is situated on the top of a prominent conical 

 hypostome. 



There are no external ridges or other markings on the body-walls. 



The genus may be defined as follows : — 



Clavulariidse forming small colonies, consisting of stiff non-retractile polypes situated 

 at considerable intervals from each other on a thick plate-like stolon. Tentacles 

 non-retractile. Pinnae few and widely separated. Spicules absent. 



One species, Stereosoma celehense. Polypes 15 mm. long, 3 mm. in diameter ; 

 tentacles 10 mm. long, with from 5 to 10 pinnae on each side. Colour pale brown. 



Locality. Shore reefs on southern part of Talisse Island, North Celebes. 



Genus Clavularia. 



Clavularia austkaliensis, Hickson ( 1 1 ), Variety A. (Plate L. fig. 3.) 



Specimen 1. Stolon thin and membranous, forming in some places sympodial plates, 

 in others broad and narrow strands. 



Polypes partially retracted into the stolon, forming protuberances on its surface, 

 0"5 mm. in diameter, 1-0 to 1'5 mm. in height, and about 2 mm. apart. 



Spicules numerous, simple, multituberculate, 0"14 to 0"18 mm. long (Plate L. fig. 4). 



Colour in spirit white. 



The specimen sent to me is parasitic on a piece of sponge. 



An interesting point in connection with this specimen is the enormous number of 

 zooxanthellae in the intermesenterial spaces (Plate L. fig. 5). 



