PROCEEDINGS OF UNITED STATES NATIONAL MUSEUM. 387 
Polycerella Emertoni Verrill, sp. nov. 
Body small, elongated-ovate, rather narrow, somewhat angular, about 
as high as broad, sometimes higher than broad, tapered and somewhat 
acute posteriorly, narrowed a little at the neck. Head high, convex 
above, sometimes bilobed, but often rounded in front, capable of chang- 
ing its form to a great extent, the part in front of the dorsal tentacles 
being capable of considerable elongation and of contracting to a truncate 
form. Foot high and narrow, obtuse posteriorly, the anterior angles 
prolonged into short but prominent auricles, often curved backward and 
pointed, at other times short and blunt. Dorsal tentacles rather long, 
not retractile, but capable of considerable contraction; in Sao 
their length is often equal to the breadth of the neck; they are fusiform 
or subclavate, blunt, smooth or showing only slight, transverse, irregular 
wrinkles, ane casas in form, sometimes nearly cylindrical, at other times 
swollen in the middle or toward the tip. Edge of the mantle indicated 
only by a slight, often crenulated, ridge along each side and around the 
head. Above this edge there is a row of small papilla, of which two on 
each side are in advance of the dorsal tentacles; two are opposite to 
them, and four or five on each side occupy the space between the tenta- 
cles and gills; a row of five or six, on each side, extends beyond the gills 
to near the end of the body, the posterior ones becoming very small. 
Behind the gills there are three or four pairs of larger and longer pa- 
pill, situated more dorsally; of these the two pairs next to the gills 
are longest, and are often nearly equal to the dorsal tentacles in size 
and length; they are usually somewhat swollen in the middle and blunt 
at the tip. Two or three pairs of much smaller papill are situated on 
the back, in front of the gills. Gills three, narrow, elongated, pinnate, 
subplumose, not fineiy divided, curved backward, not retractile, about 
equal in length to the dorsal tentacles; the pinne are few, alternate, 
generally incurved, those toward the base more slender. 
Color yellowish green to olive-green, varied with lemon-yellow, and 
blotched and specked with darker green or blackish ; foot, tentacles, 
gills, and dorsal papille lighter greenish yellow, sparingly specked with 
dark green. 
Length, 5™= to 6™™; breadth, 1™™; height, 1.12™™; length of rhino- 
phores, 3mm, 
The odontophore is very minute. The teeth of the inner row, on each 
side, are relatively very large and long, stout, with the shaft bent back- 
ward and the end abruptly curved forward and divided into two sharp 
denticles ; another sharp denticle is situated laterally, below the others. 
The two outer lateral rows of teeth are much smaller and less than half 
the length of the inner ones, nearly equal in size and form, simple, 
strongly curved forward, and very acute. 
This species was first taken by the writer at Wood’s Holl in September, 
1875, at the surface, among eel-grass; and on hydroids from the piles 
of Long Wharf, New Haven, Conn., October, 1875. At Newport, R. L., 
it has been found several times by Mr. J. H. Emerton and the writer, in 
