REPOET ON THE TUNICATA. 
215 
abdomen. These are the only genera which are very closely allied to it : the other 
Polyclinidse may be all readily distinguished from Amaroucium by the characters of the 
branchial aperture, the structure of the branchial sac, and the condition of the stomach 
and the test (consult table, p. 152). 
This genus is one of the largest in the Polyclinidse, and contains some of the 
commonest and most widely distributed forms. In addition to Savigny’s and Mdne- 
Edwards species, others have been described by Olivi, Eenier, Delia YaUe, von Drasche, 
and others, and now at least eleven new species and several varieties have been added 
by the Challenger investigations. These new species may be distinguished by means of 
the table which follows. 
It would have been much better in this and all the similar tables if I could have 
included all the known species of the genus. I have done so wherever it was possible, 
but in many cases the descriptions of the older species are so short and so imperfect 
that from the absence of any details of their structure it is quite impossible to include 
them iu the tabular schemes or assign them to their proper positions in the genus. 
Amaroucium. 
Colour white. 
I 
A. alhidum. 
Colour greyish 
or yellowish. 
Colour black. 
I 
A. nigrum. 
Ascidiozooids very 
small, less than 5 mm. 
in length. 
Stigmata well Stigmata 
developed. small. 
I I 
A. loevigatum. | | 
Colony pale Colour 
hver coloured, light grey, 
opaque. transparent. 
Ascidiozooids large, 
more than 5 mm. 
in length. 
Stigmata short Stigmata long 
and rounded. and narrow. 
^ I 
I I A. colelloides. 
Intestinal loop Intestinal 
long and loop short, 
narrow. I 
A. hepaticum. 
A. recumbens. | j 
Atrial languet Atrial languet 
long and short, 
narrow. | 
I A. cornplanatum, 
I ^ ^1 
Stomach Stomach 
spherical. cylindrical)’ 
Transverse 
vessels with 
horizontal 
membranes. 
I 
A. irregular e. 
Transverse 
vessels with 
no horizontal 
membranes. 
I 
A. pallidulum. 
A, globosum. A. variabile. 
