378 Transactions.—Zoology. 
Arr. LI.—Descriptions of three new Species of Opisthobranchiate Mollusca, 
from New Zealand. By T. F. Cuzeseman, F.L.S., Curator of the Auck- 
land Museum. 
Plate XVI. 
[Read before the Auckland Institute, 22nd October, 1877.] 
From a number of new species of Opisthobranchiate Mollusca, collected 
in or near Auckland Harbour, I have selected for description the three 
following prominent forms :— 
1. PLEUROBRANCHUS ORNATUS, n. sp. (Pl. XVI., figs. 1, 2.) 
Body 8-4 inches long, broadly elliptical, depressed, nearly equally 
rounded at both ends, colour varying from pale buff to a clear reddish 
brown, with irregularly disposed blotches of a rich dark red-brown ; mantle 
large, extending over and concealing both head and foot, quite smooth, 
margin thin, entire; dorsal tentacles short, stout, abruptly truncate, finely 
transversely wrinkled, approximate at their origin, but gradually diverging 
at their apices; colour reddish brown tipped with white; eye-specks black, 
placed a little distance behind the tentacles, embedded in the integument, 
but appearing through it; oral tentacles united in front by a thin semi- 
circular expansion which forms a veil concealing the mouth, and which is 
carried in advance of the foot; mouth roundish, with fleshy lips; buccal 
plates two, regularly reticulated; odontophore with numerous rows of 
similar unciform teeth. Branchial plume placed in the groove between the 
foot and the mantle, very large, composed of about 22-24 pectinations; foot 
oblong, thin and flexible, pale waxy white. 
Shell internal, 4 to 3 inch long, squarish oblong, thin and membranous, 
semitransparent, slightly iridescent, closely marked with somewhat irregular 
concentric strie or folds; colour varying from nearly white to pale pinkish 
or tawny brown. Spire minute, obscure, mouth occupying the whole of the 
undersurface. 
My first specimens of this handsome species were obtained from under 
stones between tide-marks in Auckland Harbour; where, however, it is by 
no means common. Near Waiwera and in some other localities on the 
Hauraki Gulf it is much more frequently met with. It is easily kept alive 
in an aquarium, but is very sluggish in its movements. 
2. PLEUROBRANCHEA NOVE-ZEALANDLE, n. Sp. (Plate XVL, fig. 3.) 
Body oval, convex, thick and fleshy, smooth and lubricous to the touch, 
but the whole surface nevertheless covered with minute puckers and folds. 
Colour light grey, copiously streaked with irregular anastomosing lines of 
dark greyish-brown, and sprinkled with numerous minute and almost 
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