OtlSTHOBEANCHIATA FROM THE ABEOLHOS ISLANDS. 551 
The penis is unarmed, the prostate large, and, according to Bergh, a 
glandula and hasta amatoria are present. 
Species Asteronotus fuscus, sp. nov. (PI. 28. figs. 12, 13 ; PL 30. 
figs. 48-50.) 
Body. The body is shaped like a typical Dorid — oval and with a moderately 
arched dorsum. The mantle is well developed, and projects considerabl}^ 
beyond the foot all round. The whole animal is like a piece of india-rubber 
to feel. The dorsum bears a series of raised elongated tubercles, the largest 
of which forms an irregular ridge stretching from between the rhinophores 
back to the branchial aperture. From this median projection a number of 
unequal and irregular short side-ridges are giv§n off, getting lower as they 
pass from the middle line, and all around the margin is a number of small 
oval or roundish tubercles. 
Colour. The colour of the preserved specimen is a muddy-brown, and 
a note included with it states that it was "dirty brown, rough surface." 
Professor Dakin informs me that it Avas of a dirty brown with some lighter 
brown spots, but no conspicuous colour-pattern. 
Dimensions. The specimen measured 27'5 mm. long by 15 mm. wide and 
9 mm. high, and the foot 24 mm. by 6"5 mm. 
Read. The head is quite small with a small mouth in the form of a short 
transverse slit, and on each side is a small tentacle. 
Foot. The foot is only moderately broad, with an undulating margin. 
The anterior end is bluntly rounded, strongly bilabiate, the upper lip is 
indented in the middle line, and the posterior end is pointed. 
Rhinophores. The rhinophore has a bluntly conical, perfoliate clavus with 
a fair number of thin leaves and a short cylindrical stalk. They are com- 
pletely retractile within cavities, whose margins are slightly raised, so that 
they look somewhat like a tubercle. In the pi-eserved specimen they are of 
a yellow colour. 
Branchice. The branchijE are five in number, each consisting of a large, 
branched, plume-like gill, arranged in a circle. They are completely 
retractile within a cavity with a raised margin, so that it stands up like one 
of the larger tubercles. The edge of this is furnished with six small lobes, 
which, when the aperture is tightly closed, are tucked inside. 
Radula. The pale yellow radula when flattened on a slide measured 3 by 
2'75 mm. and contained 38-40 rows of teeth. A median tooth is absent, and 
the number of pleurals in each row was : — in the first 6 . . 6 (z. e., 12) and in 
other rows from the third on 65.0.65 [i.e., 130). The teeth themselves 
are simply hamate and increase in size as they pass outward to beyond the 
middle of the line. They decrease in size rapidly at the outer margin, 
and the last one or two are reduced. 
The anus lies on a well-marked papilla in the middle of the branchise, and 
it bears at its base the small oval excretory pore. 
