1861.] MR. W. HARPER PEASE ON NEW MOLLUSCA. 245 



branchial plumes small, not reaching the edge of the mantle, and 

 retractile into a semicircular cavity ; plumules ten, pinnate, middle 

 ones largest Colour dark green, foot pale or yellowish, cervical 

 tentacles and branchial plumes slate-colour, dorsal papillse sometimes 

 tipped with white. 



Hab. Under loose coral on reef, Tahiti. 



The above species agrees in its generic characters with the first 

 described by me, from the Sandwich Islands, and confirms the genus 

 as then established. 



Plexjrobranchxts delicatus. 



Animal small, delicate, subpellucid, uniform orange-yellow through- 

 out, the viscera imparting a dark shade to the dorsal region ; mantle 

 smooth, oblong-oval, truncate in front, rounded behind, convex along 

 the dorsal region ; foot elongate-oval, rounded at both ends, entirely 

 concealed by the mantle. 



Shell small, elongate-oval ; nucleus subspiral, exhibiting distinct 

 lines of growth ; pale horn-colour, tinged with violet, subpellucid. 



Pleurobranchus ? 



Animal cream-colour ; mantle reticulated with opake white, and 

 irregularly maculated with reddish brown ; the larger spots more or 

 less dotted with white ; under edge of the mantle and margin of foot 

 dotted with reddish brown, and a larger spot of the same colour on 

 the upper posterior end of the foot. 



Form oval ; anterior portion of mantle concave, smooth, subpel- 

 lucid, with the exception of the white reticulations, which appear 

 slightly elevated ; foot thin, oblong, projecting behind the mantle 

 when the animal is in motion. 



Cryptophthalmus cylindricus. 



Animal elongate, smooth, subcylindrical, sides nearly parallel ; 

 cephahc disk about one-fourth of the entire length of the animal, 

 depressed, subcaudate, convexly truncate in front, and furnished 

 posteriorly with two small, appressed, triangular lobes ; eyes beneath 

 the cephahc disk inconspicuous from above, but can be seen distinctly 

 by turning up the edges of the disk ; the lateral lobes closely en- 

 velop the body, extending from the head to the excretory tube, the 

 left one overlap])ing the right ; excretory tube at the posterior end 

 of the body, short, convolute. Colour dusky olive, the margins of 

 the cephalic disk paler than centrally, and the locomotive disk paler 

 than above. 



Hab. Tahiti, on sea-weed. 



Dolabrifera tahitensis. 



Animal subpyriform, elongate, widest posteriorly, rounded behind, 

 margins thin ; dorsal region furnished with scattered, minute, sub- 

 retractile simple and branchial filaments ; head rounded above, con- 

 vex in front ; eyes immersed, a little in advance of the dorsal ten- 

 tacles, the pupil bluish black, and iris bluish slate ; dorsal tentacles 



