PLEUROBRANCHUS. 193 
Australo-Zealandic: P. punctatus, angasi, Australia. 
P. ornatus, New Zealand. 
East Indian: P. cornutus, Amboyna. 
Indian Ocean: P. peroniti, Mauritius. 
P. granulatus, Cape of Good Hope. 
P. oblongus, citrinus, Red Sea. 
P. zeylanicus, Ceylon. 
(Species of European Seas). 
P. pLuMULA Montagu. PI. 52, figs. 60, 61, 64, 65 ; pl. 74, figs. 1-3. 
Body semioval, gelatinous, lemon color, or whitish with a slight 
tinge of yellow, marked with flake-white spots, minutely tessellated 
all over with faint lines, and covered with a few scattered pustuies ; 
mantle extending on every side beyond the foot, of a reticulated and 
apparently porous texture, and occasionally puckered or raised in 
folds; it israther thin on the back and thickened at its edges, which 
are often wavy and wrinkled ; and it has asmall notch on the right 
hand side, as in Lamellaria ; the edges of the mantle are irregularly 
studded with microscopic tubercles ; head-veil or hood semicircular, 
forming a bluntly pointed flap at each side, it is carried in advance 
of the foot; head short, mouth round and open; tentacles propor- 
tionally large, but rather short, diverging at an angle of about 45° 
and projecting outwards, they are half open down the middle; tips 
obliquely truncated, eyes black, partly imbedded in the outer integ- 
ument and not always visible, placed close together on the neck 
between the tentacles at their base; foot oblong, expanded towards 
the sides, and sinuous or wavy at the edges, occupying about half 
the space of the mouth; it is squarish or gently curved and double- 
edged in front, and tapers to a rounded point behind; gill plume 
placed in the divisional groove between the mantle and foot, not 
always protruded, and never beyond the edge of the mantle, com- 
posed of about 20 sloping strands or pectinations ; it is in some indi- 
viduals reddish-brown, and in others of the same color as the rest of 
the body ; liver brown ; ovary cream color. Length 1 inch. 
Shell oval with a squarish outline, sometimes oblong, more solid 
and compact than P. membranaceus, glossy and partially iridescent ; 
sculpture, microscopic and close set longitudinal striz, which are 
more conspicuous near the spire, and are interrupted by the lines of 
growth, so as to form a series of short rows; the lines of growth are 
irregular and rather numerous, and many specimens have also a 
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