PLEUROBRANCHUS. ]93 



Australo-Zealaodic : P. pwidatus, angasi, Australia. 



P. ornatus, New Zealand. 

 East Indian : P. cornutus, Amboyna. 

 Indian Ocean : P.peronii, 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 ; pi. 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 pustules ; 

 mantle extending on every side beyond the foot, of a reticulated and 

 apparently porous texture, and occasionally puckered or raised in 

 folds ; it is rather thin on the back and thickened at its edges, which 

 are often wavy and wrinkled ; and it has a small 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 striae, 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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