Mr. Alder on the Genus Polycera. 341 
branchiz of about five pectinated branches each, the points of which 
are tipped with pale yellow. The anterior plume is longest, the 
two side ones shorter, and all having a graceful curve inwards. Sur- 
rounding these are ten linear, subclaviform, branchial appendages ; 
generally arranged five on each side, and tipped with orange or pale 
yellow. ‘The hinder part of the body tapers to an obtuse point, is 
slightly keeled, and sometimes marked with an orange central line. 
The viscera are seen in a brown or pinkish mass through the trans- 
parent skin. There is no cloak, nor are the sides of the body angu- 
lated as in the other Polycere, but gradually rounded off to the foot. 
Foot linear, narrow, grooved down the centre, and cloven at the 
hinder extremity. Nospicule. ‘The orifice of the sexual organs on 
the right side. 
A few specimens of this elegant and graceful little animal 
were found in pools among the rocks near low-water mark at 
Cullercoates. 
Occasionally this species is entirely white, the body being 
semi-transparent and the tips of the appendages opake. The 
number of branchial appendages varies, one or two of them 
being sometimes rudimentary or entirely deficient. One in- 
dividual spawned while confined in a glass of salt water. The 
spawn was deposited in a single broad gelatinous band form- 
ing a semicircle, and strongly glued to the side of the glass*. 
The pulsations of the heart varied from 45 to 75. 
_ The first of the species here described may be considered 
the type of the genus Polycera. 
The second agrees with it in the prismatic form of the 
body, and longitudinal rows of tubercles; in the presence of a 
veil and uf eyes; but differs in the number and form of the 
branchial lobes, and in having imbedded spicule. 
The third has much fewer points of resemblance ; it agrees 
with the former in general contour, in the presence of tenta- 
cular filaments and of branchial lobes ; but the prismatic form 
of the body and the lines of tubercles are no longer seen. 
The frontal veil and eyes + are also absent, and the branchial 
lobes, becoming greatly more numerous, completely encircle 
the plumes{. ‘Taken collectively, these variations from the 
* A specimen of Zolidia rufibranchialis, contained in the same glass, de- 
posited its spawn in a narrow waved thread, many times convoluted, and 
forming a pattern something like a true lover’s knot. This was in the 
month of July. . 
+ In none of the individuals I examined did I observe any appearance 
of eyes. Since the above was written, however, my friend Dr. Johnston 
had kindly favoured me with a drawing and description of a very similar 
mollusk discovered by him at Holy Island, in which he observed two 
“very minute eyes.” I must therefore admit the possibility of my having 
overlooked these obscure organs. 
t The whole three species agree in all the characters of the genus given 
by Rang, with the exception of the tentacula being “ contractiles danas une 
eavité;” a character not to be found in any of the British species. 
