1910.] FROM MERGUI ARCHIPELAGO. 803 



are airanged in two series, tlie polyps of one series alternating 

 with those of the other. The aperture faces outwards and 

 upvyards, is slightly elliptical in shape, and has an even margin, 

 indicating the boundary between tlie thicker perisarc .-ind the 

 place where the chitinous coat becomes so thin and delicate tliat 

 it follows the movements of the polyp. The perisarc throughout 

 is covered by a thin coating of extraneous material — diatoms, 

 sand -grains, fragments of sponge-spicules, and such like. 



The hydranths are much contracted, and in this state exhibit 

 a pyriform body with well-developed hypostome. The tentacles 

 appear to number about forty. 



GososoME unobserved. 



Colour, in alcohol, grey. 



Dimensions : — 



Diameter of branchlets immediately above origin 0'3I-0-38 mm. 



„ hyd ran th tube 0-25-0'31 mm. 



Hydranth, length 0-52-0-98 mm. 



„ diameter 0-21-0-42 mm. 



Nematocysts on tentacles, length 5 yu. 



,, ,, breadth 3 /x. 



Locality. Three small colonies, with hydrorhiza embedded in a 

 .«;ponge, were found at St. 35, between Warden Island, llowe 

 Island, and Lyall Island, 15 to 20 fathoms, rock and sand. 



So little is known of the variation liable to occur in the indi- 

 vidual species of this genus, that it is difficult to fix on definite 

 specific characters. In this case, I have relied mainly on the 

 structure of the tubes from which the hydranths project. In 

 the majority of the species of Corydendrium so far described 

 these are free for a considerable distance belo\v the hydranth ; 

 but here the tubes are adnato up to the end. This gives to the 

 branches a dumpy appearance, unlike the lax growth of other 

 species. In this respect it approaches most closely C corragatum 

 Nutting (1905, p. 941), which is to bo distinguished, however, by 

 its distinct " hydrophore-like structures," which are " usually 

 distinctly corrugated with deep irregular annulations" ; by the 

 presence of a well marked annular constriction near the origin of 

 the branches ; and by the largo size (5 inches) of the colonies. 



The species, Soleniopsis dendrifonnis, described by me in 1907 

 (1907, p. 491) as representing a new genu.s, under the erroneous 

 supposition that Corydendrium gave rise to gonophoros with free 

 meiiusre — I had been unable to refer to the magnificent de.scription 

 of Weismann (1883), — obviously belongs to tiie genus Cory- 

 dendrium, as Dr. Stechow has recently pointed out (1909. |>. 9). 



Corydendrium dendriformis dillers from C. parasiticum in 

 possessing thick, definite stems, with branchlets arranged in 

 pseudo-pinnate fashion, and in having the free portion of tlie 

 tubes from which the hydranths project much shorter than tiiose 

 of C. parasiticum. 



[5] 



