15 



The branchlets are curved, each consisting of a single calcareous internode varying from 1.3 

 to 1.8 cm. in length. The calyces are arranged in loose irregular spirals, the distance between 

 their bases being usually from 2 to 4 mm. They are more closely approximated on the distal 

 than on the proximal portions of the branchlets. 



The individual calyces are columnar in some cases and obconical in others. A typical 

 calyx is 4 mm. in height, with an average diameter of [.6 mm., the body being somewhat 

 expanded below. Another is much constricted below, and is 5. mm. in height and 1.7 mm. in 

 diameter at the middle. The columnar form, however, is by far the more common. The calyces 

 project at right angles from the branch, but bend somewhat upward, or distally. Their walls 

 are filled with curved spindles arranged horizontally in the basal parts and obliquely in the 

 distal parts of the walls, those on the abaxial side being larger than those on the adaxial side 

 of the polyp, and extend from the abaxial mid-line upward and obliquely around the calyx 

 walls, somewhat resembling a reversed chevron. The adaxial side is filled with smaller spicules 

 disposed horizontally, in the main. 



There is usually a crown of eight well-marked points around the margin, each point 

 consisting of the distal end of a single spicule. The tentacles bear numerous stout, bar-like 

 forms, without any very definite arrangement. 



Spicules. These sometimes attain a length of nearly 3 mm., are much more uniform 

 in size than in the other species in the collection, and are much more regularly placed, when 

 in situ, except in case of the tentacular spicules. 



Color. The colony, in alcohol, is ivory white, with light, almost white, polyps. 



A direct comparison of the Siboga material of this species with a portion of the Challenger 

 type of A. rigida, used by Dr. Versluys in his studies, shows that while the two agree well 

 in form of calyces and maximum size of spicules, they differ in comparative uniformity in size 

 of spicules in the calyx walls. The walls of A. rigida contain a few comparatively large spicules 

 on the abaxial side, interspersed with others much smaller. In A. sibogcr the abaxial wall is 

 filled with a compact series of more slender spindles of comparatively uniform size, without a 

 noticeable admixture of large and small. A. siboga differs from A. Jiorinaiii in the robustness 

 of the calyces and spicules, and from A. arbiiscula in the same points as from A. iioriimni. 

 hideed, these two latter may be identical. 



The present species differs from the next {A. weberi) in having much stouter calyces, 

 which are directed outward, and by its marginal crown of points. 



2. Acanclla weberi new species. (Plate III, figs, i, \a\ Plate V, fig. 6). 



Stat. 74. 5°3-5S., ii9°o'E. 450 meters. Globigerina ooze. 



Colony arborescent, 18.5 cm. in height. Root consisting of three (originally four) calcareous 

 cylindrical projections pointing downward and outward, all incomplete. Main stem 2.2 cm. long, 

 breaking up into a whorl of branches at its distal end, there being 5 branches in the whorl, with 



