VAN NAME: SIMPLE ASCIDIANS. 
601 
worm tubes, etc. It averages a little larger than the last species, and 
very large specimens 90 mm. long are not infreciuent from northern 
localities. 
Regarding its color Verrill (1871a, p. 99) says : " Color of the younger 
specimens pale, translucent greenish or yellowish gray, or light horn- 
Text-fig. 42. — Phallusia prunum (Miiller). X 1.7. 
color, the mantle and dark intestine distinctly visible through the 
test; large specimens are darker greenish or olive-color, generally 
becoming more or less rusty brown or russet. Mantle finely speckled 
with raised yellowish points." 
This species having been carefully described by a number of writers 
(see Hartmeyer, 1903) it will suffice here to note some of the important 
characters and the most conspicuous differences distinguishing it 
from P. ohliqua. 
Tentacles forty or more, of three sizes (in large individuals four sizes) 
arranged with considerable regularity. 
Orifice of dorsal tubercle crescent-shaped, U- or V-shaped, or some 
simple modification of these forms. In one individual it was distinctly 
Y-shaped. 
Dorsal lamina with distinct teeth corresponding in position to the 
origin of the transverse vessels. In the posterior region these teeth 
are of considerable size and themselves bear small slender teeth on 
their edges. 
Branchial sac more conspicuously fluted or plicated than in P. 
ohliqua. As the larger transverse vessels do not take much part in 
this plication a series of hollows or cavities often results, rather than a 
