176 
THE VOYAGE OF H.M.S. CHALLENGEE. 
and the base is wide and spreading. This last character, however, is probably due to the 
circumstance that the colony is attached to a fragment of a large Balanus instead of 
being imbedded in the sand. The colour is much paler than in Atopogaster elongata, 
the test being of a dull whitish-grey, upon which the Aseidiozooids show as opaque 
yeUowish-grey spots. The surface although uneven is in some places very smooth and 
glistening. The Aseidiozooids are small and numerous, and are scattered irregularly 
over the surface just as in the case of Atopogaster elongata. They are more numerous 
at the upper end of the colony than near the base of attachment, and this causes a slight 
difference in appearance ; the lower part being greyer in colour. 
The Aseidiozooids are elongated antero-posteriorly, are usually about 3 or 4 mm. in 
length, and are not clearly divided into regions. The widest part is about one-fourth of 
the way back, and the post-abdomen occupies the greater part of the body and is of 
considerable thickness. The whole body is quite opaque. 
The test cells are rather large (PI. XXIV. fig. 10, t.c.), and have usually a granular 
appearance. The opacity of the test is probably due in great part to the abundance of 
these cells. The shape of the cells, which are ovate or rounded, is quite different from 
that of the test cells in Atopogaster elongata, where the elongated fusiform cells give 
a characteristic appearance to sections of the test (compare PI. XXIV. fig. 5 with 
PI. XXIV. fig. 10). 
The mantle is very like that of Atopogaster elongata. There are usually three or 
four muscle fibres in each of the longitudinal bands. 
The branchial sac is rather smaller and the stigmata more rudimentary than in the 
case of Atopogaster elongata. The alimentary canal forms a short loop. 
In other respects this variety appears to agree closely with the specimens of the 
species from Station 313. 
Morchellioides, n. gen. 
Colony massive, sessile. 
Systems compound, inconspicuous. 
Aseidiozooids elongated, but not distinctly divided into regions. Branchial 
aperture eight-lobed. 
Test gelatinous. 
Branchial Sac large and well developed. 
Alimentary Canal large. Wall of stomach irregularly thickened. 
Post- Abdomen large, but not distinctly separated from the abdomen. 
The species for which this section is proposed agrees with the genera Morchellium, 
Giard, Synoicum, Phipps, and Sidnyum, Savigny, in having the wall of the stomach 
