84 
SPOLiA ZEYLANICA. 
altogether in one, in another they form a continuous and regular 
line from the branchiae forwards. In the rest they consist of 
patches, generally arranged so as to form a more or less interrupted 
medio-dorsal line, but occasionally are scattered over the sides as 
well. They look as if the animal had been sprinkled with sand, but 
are due to the entire absence of pigment in certain areas of the dorsal 
surface, both in the depressions and in all the tubercles, large and 
small. 
The animals present the general appearance of a heap of tufted 
seaweed. This is due to the back being thickly covered with 
compound tubercles of very irregular shape, the largest about 
5 mm. high, but often greater in breadth than height. In shape 
they are roundish and somewhat flattened at the tops. They bear 
a variable number (5-25) of flat knobs, and on each of these knobs is 
set a group of very small cylindrical papillae, from which sometimes, 
but not always, a few spicules project a little. But the shape of the 
tubercles shows infinite variety, and is not even constant in one 
specimen. Sometimes the raised patches which bear the papillae 
are set on the flattest parts of the dorsal surface, sometimes the 
tubercles are flat, and sometimes they are conical. When large, they 
may often be described as four-fold, that is to say, a roughly conical 
tubercle develops bulges at the side ; on these bulges are set flat 
prominences, and on the flat prominences are set the papillae. All 
the tubercles and integuments are very soft and flabby. The 
margin of the foot has a shallow groove in front, and the upper 
lamina is divided in the middle ; the two lappets thus formed run 
up to the mouth on either side. In many specimens no tentacles 
are visible. In others it is plain that there is a long tapering well- 
formed tentacle near the point where the lappet joins the lips. As 
may be imagined from the luxuriantly tuberculate character of the 
back, the rhinophores and branchiae are not conspicuous. The 
sheaths of the rhinophores are raised, and sometimes as much as 
5 mm. high ; the surface is tuberculate and the margin very irregular. 
In some specimens it is edged with a row of small white papillae. 
The branchial pocket is also raised, tuberculate, and irregularly 
lobed. The rhinophores are dark, with white tips. The branchiae 
are 5, tripinnate, and dark, with a variable amount of white colour 
on their inner sides. They are united at the base. The general 
impression produced by the animals, particularly by those which 
have the white line on the back most perfect, is that there is a 
median dorsal ridge or keel. But this impression depends largely 
on the white line. The dorsal keel is irregularly and sometimes very 
slightly developed, and in one specimen is entirely absent. The 
foot is broad and pellucid, with little colour of its own, but often 
covered with minute brown dots. 
Immediately behind the lips on the outer wall of the mouth tube— 
that is, on the surface turned towards the body cavity and viscera— 
