50 



The individual calyces are quite small dome-shaped verrucae when the polyps are 

 completely retracted, and short tubes when they are completely expanded. They are so closely 

 crowded on the surfaces of the branches as to be contiguous at their bases. A typical one 

 measures .9 mm. in diameter at the base. The height varies in accordance with the state of 

 expansion of the polyps, but seldom exceeds i mm. The calyx walls are armed with very 

 jagged spindles and Blattkeulen and, in certain stages of contraction of the polyps, the margin 

 is distinctly 8-lobed. The polyps have a rather slender collaret, above which the spindles form 

 eight points. Beyond these points there are a few longitudinal spindles, lying along the dorsal 

 surfaces of the tentacles. Minute spindles also extend from the dorsal surfaces diagonally to 

 the pinnule bases. 



S p i c u 1 e s. The most characteristic forms are remarkable Blattkeulen which consist of 

 a tuberculate base from which project a number of parallel flattened finger-like points. Or they 

 may be likened to a plate which has been shattered by several vertical fissures. There is 

 complete intergradation between these Blattkeulen and typical Stachelkeulen, so that it is hard 

 to differentiate them. Besides these curious forms there are regular spindles often curved, from 

 the polyps, and clubs, besides a great variety of nondescript forms. 



Color. The colony is a rather dull yellowish brown. The spicules are colorless. 



3. Mopsella spongiosa new species. (Plate VIII, figs, i, i, Plate XII, fig. 7). 



Stat. 273. Anchorage off Pulu Jedan, East coast of Aru Islands (Pearl Banks). 13 meters. 

 Sand and shells. 



Colony strictly flabellate and reticulate, spongy in texture and not so delicately branched 

 as in the other species, although the meshes are fine. Height of colony 21.5 cm. Spread 20 cm. 

 The main stem is irregular in section, but not appreciably flattened, and is 14 mm. in diameter. 

 About 1 8 mm. from its base it breaks up into numerous branches which redivide to make the 

 mesh. In the main stem the nodes and internodes are hardly distinguishable. In one of the 

 main branches the proximal node is 7.5 mm. long and 5 mm. in diameter, while the proximal 

 internode is 2.3 mm. long and 3 mm. in diameter. The nodes are much swollen and longer 

 than the internodes throughout the basal parts of the colony. A node near the edge of the 

 fan is 4 mm. long, while the internode just below it is 1 1 mm. long and 1.6 mm. in diameter. 

 Most of the branches are somewhat flattened, but the distal twigs are round. The meshes are 

 small, usually oblong, and the anastomoses are usually, but not always, at the nodes. The 

 calyces are emplanted very thickly on these sides of the main branches and on all sides of 

 the distal ones. 



Spicules. The most typical form of spicule in this species is the foliaceous club, with 

 an irregular densely tuberculate basal part and a distal portion consisting of several flattened 

 expansions usually extending parallel to each other and often in the same plane. Frequently 

 these take the form of coarsely tuberculate spindles from one side of which the foliaceous 

 expansions arise, making "unilateral" spindles. These Blattkeulen are exceedingly varied in 



