PORAMINIFEHA— HEKON-ALLEN AND EAV.LAND. 79 



thin external cliitinous meiiibraiie. Apertures terminal. sini])le or fimiislied with 

 a radiating corona of spicules. Very brittle when dry. but probably more or less 

 flexible in the living state. No perfect .specimens were received. 



The basal pad (Fig. 12a) is normally composed of fine grey mud and acicular 

 spicules, both entire and broken. The spicules are arranged with some regularity, 

 converging towards the raised centre of the pad from which the main trunk 

 arises. When attached to a plane surface the basal pad is amoeboid in outline, 

 but otherwise it conforms to the contour of the host. It is easily detached, 

 and when mounted in balsam (Fig. 17) exhibits a number of branching tubes, 

 originating in one or nuire central cavities and radiating, as in Masonella, 

 towards the edges of the pad, but having no visible external apertures. 



These basal cavities are sometimes, but not always, visible when the mider 

 surface of a detached pad is examined. It seems probable that the specimens 

 thus exhibiting the basal cavity have become broken in detachment, leaving the floor 

 of the basal pad attached to the host. 



From the central cavities of the pad originates the hollow trunk (Fig. \2b) 

 which rises from the pad and varies greatly m appearance. More than one trunk 

 may rise from the same pad (Fig. 12c). Normally the trunlc takes the form of 

 a thick-walled tube, gradualh- dinunisliiug in diameter and furcating at irregular 

 intervals, each branch again dividing into smaller branchlets (Fig. 12e), but 

 remaining unseptate throughout (Fig. IS). 



The trunk may, however, terminate while still unbranched (Fig. 12c), endmg 

 with a terminal crown of radiating sponge-spicules which no doubt serve as 

 supports for pseudopodial extensions, as in Marsipella cylindrica, Haliphysema 

 tumanowiczii, and other species. A sunilar terminal appendage may occur on a side 

 branch after furcation of the nuxin trunk (Fig. 12d). 



No complete branching specimens have been found presenting an unbroken 

 terminal extremit}'. and the nature of the orifice at the end of the small branchlets 

 remains to some extent problematical. They may end in a simple constricted 

 aperture, but it is more probable that they terminate in a more or less loosely 

 agglomerated and radiating crown of projecting spicules, as does Marsipella 

 cylindrica, which is of about the same diameter. There can be no doubt that 

 the extraordinary terminal fragment (Fig. 12f) reproduced in our plate belonged to 

 our species, but the proportion of spicules to cement is higher than was observed 

 in any other fragment, and it must be regarded as abnornuil. 



A certain number of basal poitions have been fmmd which exhibit little 

 or no evidence of a sessile condition and which show signs of modification of 

 structure as a result. Whether the organism ever exists in an entirely fre( 

 condition is uncertain. Most of the specimens suggest attachment in some form 

 or other, if only to loose sand. In one instance the test is attached to the free 

 tube of an Annelid, and probably started its growth later than the worm. 



