OPISTHOBRANCHIA.TA FROM THE ABROLHOS ISLANDS. 563 
protuberances, giving them a very uneven appeai-ance. The large projections 
also have smaller ones near their bases, and similar small ones are scattered 
over tlie general dorsal surface. Three noticeably large projections lie on 
each side between the i-hinophore and the gills, and two more are situated 
betvi'sen the rliinophores. 
Colour. The general body-colour o£ the preserved specimen is a dirty 
yellovifish grey, becoming darker towards the periphery. Down the middle 
of the back is a series of three large roughly rhomboidal black marks, which 
have other veryidark, almost black, markings within them. Five or six similar 
but slightly smaller marked areas lie lateral to the large projections on each 
side, the first pair of lateral marks being in front of the rhinophores and the 
last behind the branchiae. The clavus of the rhinophore is light-coloured 
and the tips of the branchiae very dark ; Professor Dakin iiiforms me that in 
life the pattern was similar, but the colours brighter and the contrast more 
marked. 
Dimensions. The preserved specimen measured 72 mm. long by 40 mm. 
wide (mantle extended) by 17 mm. high. The foot measured 65 mm. long 
by 15 mm. wide, so that the mantle, when extended, projected 12"5 mm. 
beyond the foot. 
Head. The head is extremely small and inconspicuous, and the mouth is a 
tiny aperture lying between the two edges of the front end of the foot. On 
e:ich side of the head is a tiny flap-like tentacle about 1'5 mm. long, partly 
retracted within a shallow groove-like cavity. 
Foot. The foot is well developed, long, fairly narrow, and with an expanded 
flange-like margin. At the anterior end the foot bears a deep longitudinal 
cleft, between the edges of which lies the mouth. 
Rliinophores. The rhinophores are fairly small clavate structures with a 
perfoliate clavus, and are entirely retractile within cavities provided with an 
elevated tubular margin. They lie fairly close together near the anterior 
end. 
Brancliice. The five branchial plumes are tripinnate and ari-anged in a 
fiiirly close circle, with a tendency to fusion at their bases. Each is dendri- 
form. They are retractile within a wide sliallow cavity with a slightly raised 
margin. 
Radula. No trace of a radula or phar3mgeal complex is present, and the 
first part of the oesophagus is in the form of a straight narrow tube. 
The anus lies between the bases of the two hindermost gill-plumes upon a 
fairly well-developed sub-conical papilla. 
The genita aperture is, as usual, high up on the right side of the body 
about one-quarter of the way from the anterior end. 
Notes. Only one specimen is represented in the collection with a label 
" Nudibranch from Fremantle, W.A." It is not therefore an Abrolhos 
type, so far as we know. 
40* 
