VAXXAME: COMPOUND ASCIDIANS. 347 
and a southern one composed of 
Botnjllus schlosseri (Pallas). 
Perophora viridis Verrill. 
Didemnum lutarium sp. nov. 
Amaroucium pellucidum (Leidy). 
Amaroucmm stellatum Verrill. 
Cape Cod may be said to be the dividmg limit between the areas 
occupied by these groups, but no exact limit can be laid down, as manv 
of the species extend a considerable distance into the territory of the 
other group. All the species of the northern group range northward 
beyond the limits of the region Avhich this paper covers, and if not 
found in Europe also, are represented there by scarcely distinguishable 
aUies, while of the southern group BtdrijUus schlosi^cri only is also 
European, unless future investigation should prove that one or more 
others are inseparable from European forms. 
But little has been recorded concerning the distribution of com- 
pound ascidians on the American Atlantic coast south of Xew England, 
and the southern limits of the range of the southern group of species 
remain to be determined. Perophora viridis is the only one of them 
recorded from Bermuda, though a species of Didemnum closely allied 
to D. lutarium is also foimd there. Auiaroucium stellatum (by Coues 
and Yarrow), .J. pelluridum (by Verrill), and Perophora viridis (by 
Lefevre, and Wilson), have been recorded from North CaroUna, but 
from the northern part of Xew Jersey southward until the region of 
coral reefs is reached, the shores and bottoms are chiefly of shifting 
sand, unfavorable for the growth not only of ascidians but of most 
other marine organisms except the comparatively small percentage 
which are especially adapted for life in that environment; while the 
bays, sounds, and harbors are in many cases too brackish to be 
favorable for organisms so strictly marine as the ascidians. Yet the 
reports of several zoologists (Stimpson, Coues and Yarrow, Lefevre, 
Wilson) show that ascidians are abundant about Beaufort, North 
Carolina, and no doubt investigation would result in finding other 
favorable localities along this stretch of coast. 
Distribution in Depth. 
The species of the first or northern group all occur through a con- 
siderable range in depth, being found from a depth of a few fathoms 
