204 PLEUROBRANCHUS. 



more obtusely rounded before than behind. Surface above convex, 

 and coarsely marked with concentric wrinkles ; nucleus posterior 

 and lateral, forming a small cavity at that portion of the shell. 

 Length 5 lines (Pse.*). 



Sandwich Is. (Pse.) 



Pleurobranchus pellucidus PSE., P. Z. S., 1860, p. 24. 



P. MARGINATUS Pease. 



Form oval, smooth, convex above and subpellucid. Mantle 

 widest at the middle, rounded behind and truncately rounded in 

 front, and concealing the foot. Tentacles rather long, stout, grooved, 

 truncated, and cylindrical. Oral veil triangular. Foot oblong 

 oval. Color pale lemon yellow, freckled with white and mar- 

 gined with light red. Shell ovate, thin, fragile, pellucid, whitish 

 horn-color, with a dull red tinge near the nucleus. Nucleus sub- 

 spiral. Striae of growth coarse. (Pse.). 



Sandwich Is. Under stones in the lower region of the littoral 

 zone (Pse.'). 



P. marginatus PSE., P. Z. S., 1860, p. 25, No. 18. 

 P. RUFUS Pease. 



Form oval, smooth and convex above. Mantle concealing the 

 foot, widest at the middle, rounded behind, and somewhat concave in 

 front. Tentacles stout, truncated, grooved and cylindrically taper- 

 ing. Oral veil subtriangular. Branchiae tripinnate, with the 

 pinnae arranged alternately. Foot oblong oval, rounded at both 

 ends. Color uniform vermilion. Length 1 inch. (Pse.'). 



Sandwich Is. Under stones in the lower region of littoral zone. 



P. rufus PSE., P. Z. S., 1860, p. 25, No. 19. 



P. VARIANS Pease. 



Oval, rather rugose, convex above. Mantle rounded behind, 

 deeply sinuose in front, and margins slightly undulated. Tentacles 

 arising from the head, curving laterally, deeply grooved below, 

 truncated, cylindrically tapering, transversely lamellated. Eyes at 

 their posterior bases. Oral veil large, convex in front, and much 

 dilating laterally, where it is deeply grooved. Mouth proboscidi- 

 form. Branchial plume simple, pinnate on the middle of the right 

 side. Foot large, reaching the edge of the mantle laterally and 

 behind. Color varying ; some bright red, others lemon-yellow, or 

 purplish brown, others again variegated with whitish ; beneath 



