80 "TERRA NOVA" EXPEDITION. 



These free or semi-free specimens differ from tlie fixed type in the sliape 

 of the initial portion wliich. instead of being an outspreading pad, takes the 

 form of an irreguhir fmlh with comparatively thin walls and a large internal 

 cavity (Figs. 11,16). The cavity is usually undivided, but is sometimes iilled with a 

 labyrinthic agglomeration of large sand-grains, the interspaces of which are probably 

 liomologous with the branching passages in the basal pad of the sessile form. 



The external wall of tlie bull) is often furnished witli projecting spicules 

 (Fig. 16), which may serve the purpose of anchoring the Indb in an upright 

 position in the mud of the sea-bottom. Occasionally there are accessory simple 

 orifices on short tubular outgrowths. The proportion of spicules to grey mud and 

 cement is noticeably less in the early stages of the Indljous form than in the 

 sessile type. 



Following the bulbous initial portion the plan of growth follows the normal 

 plan, the trunk rapidly diminishing in diameter to the first furcation and the 

 proportion of spicular material simultaneously increasing (F^ig. 11). 



There can be no doubt as to the affinities of this striking species. The unseptate 

 columnar tube and the branchmg passages of the basal pad mark it uncpiestion- 

 ably as an Astrorhizid, and, except in the existence of this specialised base and 

 the neat construction of the test, our species is evidently closely allied to Dendro- 

 phrya erecta, Strethill Wright. The structure of the basal pad so closely resembles 

 Masonella. as to indicate that the genus forms a connecting link between the 

 genera Astrorhiza, Masonella, and Deiidrophrya. 



The species occurs only in material from the New Zealand area, but is probably 

 abundant in suital)le localities. A considerable num])er of fragments have been found, 

 but no perfect specimens, owing to the character of the material. The largest number 

 of fragments were obtained at Station 6. 



At Station 4 the spicules were abnormallv large as compared with the 

 tliameter of the branches into which they were built (Fig. 14). In one fragment, from 

 Station 6, the spicules are arranged spirally (Fig. 15), as in Marsipella spiralis, 

 H.-A. & E., thus departing from the normal method of inlaying them parallel 

 to the axis of the branch. 



Size, — The maximum height of a perfect specimen can only be estimated, but 

 probably it may attain 5 or 6 nnn. The basal pad of sessile specimens ranges 

 up to 2 mm. in diameter, and the ])ulbous base of free specimens up to 1-30 mm. 

 The tubes vary between 10 and 70 mm. external diameter, according to their 

 proximity to the base. 



75. Dendronina arborescens, var. aniurctica. nov. I'l. II. figs. 13, lU. 

 Basal pad small, labyrinthic, surmounted by a short, stout trunk roughly 

 constructed of sand-grains, spicules and cement. Surface smoothly finished. 

 Colour dark grey, due to the minerals incorporated in the cement. 



