214 
THE VOYAGE OF H.M.S. CHALLENGER. 
Amaroucium, Milne-Edwards. 
ApUdium, Savigny, Memoires, 1816. In part. 
Amaroucium, Milne-Edwards, Observations, &c. In part. 
Amouroucium, Forbes, British MoUusca, vol. i. p. 15, 1853. In part. 
Amaroucium, Giard, Eecherches, &c., p. 636, 1872 (as a subgenus). 
Amaroucnim, Delia Valle, Contribuzioni, &c., 1877 (as a subgenus). 
Amaroucium, von Drasche, Die Synascidien, 1883 (as a subgenus). 
Colony massive, sometimes lobed or pedunculated. 
Systems compound and irregular. 
Ascidiozooids elongated ; branchial aperture six -lobed ; atrial usually provided 
with a long languet. 
Test gelatinous' or cartilaginous. 
Branchial Sac moderately developed. 
Alimentary Canal of moderate size ; stomach-wall folded longitudinally. 
Post- Abdomen large. 
Sa^dgny, on account of all his material having been preserved in alcohol, erroneously 
described his genus A'plidium as having no common cloacal cavities, and when Milne- 
Edwards some years later worked at the Compound Ascidians of the Chausey Archipelago 
and some other parts of the coast of France in a fresh and living condition he found that 
none of the species he examined belonged to the genus ApUdium. All of those which in 
other respects agreed with that genus differed from Savigny’ s definition in having 
common cloacal apertures. Consequently he established for those forms the genus 
Anmroucium, agreeing with ApUdium in most respects, but having common cloacal 
cavities in the systems. 
As no species of ApUdium in Savigny’s sense have since been found in a living 
condition, it is very probable that, as (4iard has suggested, the apparent absence of common 
cloacal cavities in spirit-specimens is a result of contraction after death, and that 
Savign)r’s species of ApUdium really had the cavities, and that therefore Milne-Edwards’ 
Amaroucium was unnecessary and is merely a synonym of ApUdium. Giard, 
however, in subdividing the Polyclinidse into genera and subgenera, has retained 
the name Amaroucium for one of the latter. Its characteristics are the long Ascidio- 
zooids, the six-lolDed branchial aperture, the anteriorly placed atrial aperture provided 
with a long atrial languet, the longitudinally folded stomach-wall, and the sessile and 
greatly elongated f)Ost-abdomen ; for a discussion of its exact relations to ApUdium in 
the restricted sense, see under that genus, page 200. 
Amaroucium is distinguished from Sigillina, Savigny, by its unlobed atrial aperture 
and Ijy the possession of a large atrial languet ; while from Polyclinoides, von Drasche, it 
differs mainly in not having any constriction between the abdomen and the post- 
