408 PROCEEDINGS: BOSTON SOCIETY NATURAL HISTORY. 
tie with minute opaque white 
specks. In some specimens the 
cloacal chamber or 'atrium' 
contained three or four bright 
purple tadpole-shaped larvae" 
(Verrill and Smith, 1873). 
The zooids are generally ar- 
rane;ed in rather irregular and 
extensi\e systems, though small 
circular or oval groups also oc- 
cur. The limits of the systems 
are often difficult to make out. 
The zooid here figured (text-fig. 
23) measured about 4 mm. in 
length without the post-abdo- 
men, and may be considered as 
of average size. The post- 
abdomen may be 10 mm. or 
more long when the reproduc- 
tive organs are well developed, 
but its length and thickness are 
not specific characters on which 
any reliance can be placed. 
The mantle contains distinct 
transverse muscle bands on the 
thorax underlying the more con- 
spicuous longitudinal ones. The 
latter are not placed very close 
together, and as usual are most 
conspicuous on the thorax, grad- 
ually disappearing on the post- 
abdomen. Large rounded dark 
colored cells occur in the mantle ; 
in some individuals in abun- 
dance, in others in only small 
niunbers. The branchial orifice 
has six short lobes, each of which 
may be slightly cleft (see text- 
fig. 23); the atrial orifice has 
Text-fig. 23. — Amaroucium pellucidum 
(Leidy) form consteUatum (Verrill). Zooid. 
X 34. 
