290 MR. H. N. MOSELEY ON TWO NEW 



into a slightly prominent, rounded ridge running round the periphery of the entire hasal 

 area, and, further, is indented slightly opposite the interspaces between the long conical 

 processes, so as to have an undulating outline. Towards one end of the base (which 

 end of the animal will be termed anterior, since it is that in which the nerve-ganglion 

 lies), and in the middle line, is a prominence, also oval in outline (fig. 7, pa). This pro- 

 minence is formed of a process of the basal part of the test. It terminates outwardly 

 in a tangled mass of rootlets, massed amongst which was found much sand and shell- 

 particles from the bottom. The Ascidian was evidently attached by this process or 

 pedicle. 



Above the margin of the base the body of the animal is somewhat contracted, but its 

 walls then again spread outwards and extend into eight wide conical processes. The 

 processes terminate in abruptly narrowed tentacular-like tips (fig. 7, t, t), which are im- 

 perforate, and in which no sense-organ or any special structure could be discovered. 



On the upper aspect of the body the eight conical processes are directly continuous 

 with the upper surface, which is somewhat hollowed or saucer-shaped. 



Towards its anterior part in the middle line the upper surface is perforated by a trans- 

 verse slit, the inhalant aperture (fig. 8, id). The exhalant aperture is situated in front of 

 this, and at a lower level, proceeding from the wall of the body just above the base as 

 a short cylindrical tubular process (figs. 7 & 8, ea). The inhalant aperture is enclosed by a 

 pair of simple rounded lips, and is without tentacles. 



The test forms a wide cavity, which extends freely into the capacious hollow conical 

 processes. The two apertures, inhalant and exhalant, form the only communication 

 between this cavity and the exterior. 



A flat horizontal membrane is stretched across the test-cavity in such a manner as to 

 separate off an upper chamber communicating with the inhalant aperture from a lower 

 communicating with the exhalant. This membrane, in the central region of the body, is 

 thick and of an opaque white colour (fig. 9, g). This thickened central portion runs out 

 peripherally into eight processes, directed to the intervals "between the long conical pro- 

 cesses of the test. Opposite these intervals the processes become attached, or give origin, 

 to bands of muscular fibres, which bands, after a short radial course, in which their 

 fibres remain parallel, split into two halves (fig. 7, rm). The halves of the bands diverge 

 at an angle from one another, and proceed to the tips of the long conical processes, where 

 each is joined by the tip of a corresponding half-band from the next adjoining process. 

 The half-bands, as they run towards the tips of the conical processes, give off a series of 

 transverse muscular threads, which, passing from band to band, form a series of loops 

 one beyond the other, continued almost to the tip of the conical processes. These radial 

 muscles are apparently the homologues of the longitudinal muscles of ordinary Ascidians. 

 They would become longitudinal were the upper part of the discoid body of the animal 

 drawn upwards, so as to make the respiratory cavity tubular instead of saucer-shaped. 

 A second series of muscular threads lies beneath the radiating bands just described 

 about their points of bifurcation, and extending thence almost to their points of origin. 

 This second set of muscles takes a circular direction (fig. 7, cm), and is continued round 

 the entire circuit of the animal, the several strands, of which there are about twelve. 



