MR. MACDONALD ON A NEW GENUS OF TUNICATA. 79 
51’ 8., long. 159° 28’ E.) was a very remarkable Ascidian, which, 
as it appears to be quite new, merits brief notice. 
The external appearance of the animal so much resembled 
the nidamental case of some large Gasteropod, affixed to a 
block of coral, that no suspicion of its real nature was entertained 
until it had been minutely examined. Soon, however, it was 
ascertained that within a thin coriaceous test, fashioned like a 
snuff-box, with a perfectly applied lid, a little tunicary was en- 
closed, enjoying the power of opening and closing the operculum 
or door of its retreat at will. 
The case (figs. 1 & 2) was about $ an inch in length, and over 2 
of an inch in breadth, though rather fuller in front than behind. 
The attached side was flat (fig. 2), but the free surface (equivalent 
to the right side of the recumbent animal) was convex and rounded 
(d) ; so that the aperture at the anterior end presented a D-shaped 
or semicircular figure (fig. 4) ; and this was accurately fitted with 
a lid of a corresponding shape. The free margin of both the aper- 
ture and the lid was beset with minute and rigid spines, having an 
inward curvature protecting the entrance from invasion. In con- 
tinuity with these margins a thin layer of test-substance was 
traceable as a kind of conjunctiva (fig. 4c), upon the anterior 
part of the contained animal, to the borders of the branchial (d) 
and cloacal openings (e), which occupied the same plane in the 
mouth of the cell, being merely divided by a narrow transverse 
depression. Both these openings were simple though somewhat 
puckered in the contracted state, and encircled at a little distance 
from the free edge by a broad band of pale-red pigment. 
The mantle was closely applied to the inner surface of the test, 
without, however, giving off any palliovascular processes. A dark- 
coloured reticulation, visible through the outer epithelium, marked 
off the distribution of the blood-vessels ; and the disposition of the 
internal organs was traceable through the semitransparent tissues 
(fig. 3). 
Not wishing to destroy the specimen, I did not determine the 
arrangement of its respiratory membrane; but I observed that 
the branchial orifice was guarded by a circle of simple tentacula 
(fig. 4 d). 
_ The esophagus was short, soon opening into a subglobular’ 
stomach with thick glandular walls thrown into longitudinal folds. 
The intestine proceeded from the posterior end of the stomach, 
around which it turned inferiorly, and having coursed forwards to 
within a short distance of the cloacal opening, it ended in the vent. 
