S1 st MA Y 1824. LIII. Descriptiom of several new Species of Ascidia. B 9 C. A. LvsuEva.* Gr~Ntrs ASCIDIA, Lin. I. A SCIDIA atra. Bod 9 subcylindrie, elongated, arquated, ~" sessile ; the superior part more slender, terminated by two unequal tubes, slightly separate and parallel; these tubes have each a terminal opening, which in the shorter tube is closed by five, and in the longer one by six, triangular valves; the substance of the exterior sac is very firm, almost smooth, opaque, and very deep violaceous or blackish.mIt occurs attached to rocks, amongst Opuntiw, many species of Sertulariw, and broken shells. Its position is inclined, being adherent 10)" the side of the base, which is a little more inflated than the other parts of the body.-We observed this species at the isles of St. Vincent and Guadaloupe, where, however, it is rather rare. Whilst dredging in the bay of Calicoua, we drew this species from the bottom of the water, with many other objects, amongst which was a beautiful Holothuria, marbled with brown, red, white and blackish, which had the property of dissolving so rapidly as to be observed with difficulty. 2. A. cavernosa. Bod 9 oblong, irregular, terminated by two unequal tubes; that of the branchia and mouth nmch longer than the other, and directed upwards; that of the oviduct and excretions situated at the base of tile first and lateral; their apertures are entire, without marginal elevation, or apparent hair, and of a deep colour within ; the exterior envelope is coriaceous, thick, very firm, opaque, rugous and folded, particularly towards the base, where the folds, united in thseiculi, form three points of attachment, by means of which the animal secures itself' firmly to the interior of cavities in rocks and old madrepores; the colour is that of burnt terra