VAN NAME: COMPOUND ASCIDIANS. 405 
1872. Amouwucium pellucidum Vcrrill, Amer. Journ. Sci., ser. 3, vol. 3, p. 211. 
1873. Amaroecium pellucidum Verrill and Smith, Report on Invertebrate 
Animals of Vineyard Sound, pp. 703 (397), 401 (411, 415), 419 (424). 
1879. Amoroecium pellucidum Verrill and Rathbun, Proc. U. S. Nat. Mus., 
vol. 2, p. 231. 
1889. Amoroecium pellucidum McDonald, Rep. U. S. Comm. Fish and Fish- 
" eries for 1886, p. 858. 
1891. Amaroucium pellucidum, Herdman, Journ. Linn. Soc. London, ZooL, 
vol. 23, p. 628 (listed under heading "unrecognizable Polyclinidae"). 
1900. Amaroecium pellucidum Metcalf, Zool. Jahrbiicher, Anat., vol. 13, 
p. 526. 
1909. Amaroucium pellucidum Hartmeyer, Bronn's Tier-reich. vol. 3, suppl., 
pp. 1477, 1481 (listed as uncertain species). 
The two most striking characters which serve to distinguish this 
from the other New England members of the genus are the subdivision 
of the colony into small lobules and the dense and even coating of 
sand with which the whole or nearly the whole external surface is 
generally covered. Aplidium pallidum is occasionally conspicuously 
incrusted with sand, but rarely to such an extent as is usual and normal 
in the present form, where the sand covers the surface so thickly that 
the true character of the test is entirely obscured. Where the coating 
of sand is abraded or wanting, the test is seen to be translucent and 
gelatinous. In such cases, there is a tendency of the lobules to be 
more or less fused or united, and the specimen then approaches the 
form consicllatum (described below) in its characters. In colonies 
which are thickly incrusted with sand, the sand grains are often 
present in great abundance in the deeper portions of the test as well 
as on the surface, making the test hard and easily broken. 
The large rounded masses in which this form is often found exceed 
in bulk the colonies of the other New England species of the genus. 
They often reach 160 to 200 mm. in diameter and 70 or 90 mm. in 
height, being sometimes almost perfectly hemispherical. These 
large masses are subdivided into or built up of elongated lobules, which 
arise from the common base of the colony as narrow stalks and in- 
crease gradually in diameter as the upper part of the colony is ap- 
proached, their truncated upper extremities forming the free convex 
surface of the colony. So closely do these lobules fit together that the 
clefts between them, although they extend nearly to the base of the 
colony and are lined with the coating of sand mentioned above, show 
but slightly unless they are opened out and the lobules separated by 
