86 
THE VOYAGE OF H.M.S. CHALLENGER. 
This specimen, which was very well preserved and only slightly hardened, was 
nearly 4‘5 cm. long by 1’8 cm. broad and 1'2 cm. high. The breadth of the mantle- 
border came to 4'5 mm., of the foot to about 12 mm. ; the length of the tail was 5 mm., 
the diameter of the transversely oval branchial opening nearly 8 mm. ; the height of the 
retracted rliinopliores was 4 mm., of the retracted gill nearly 5 mm. ; the length of the 
tentacles 3 mm. ; the largest dorsal papillae were 1 '3 mm. in diameter, and almost the 
same in height. The colour of the animal was yellowish throughout ; in front and on 
the lateral portions of the back ochre-yellow, so too on the upper sides of the pedal 
border, but rather paler ; the rhinophores and gill were yellowish- white. 
The form of the body was an elongated oval, the border of the mantle not broad, rather 
powerful. The bach, which is slightly convex, is entirely covered with (PL I. fig. 2) 
papillae of various sizes 1 lying closely together, the smallest chiefly on the margin of 
the mantle. The rhinophor e-openings, which lie pretty near the front, are roundish ; 
the margin, which hardly projects at all, is furnished with small papillae. The rhinophores 
are powerful ; the club with about thirty to forty broad leaves, and with small terminal 
papilla. The transversely oval, wide branchial opening has a somewhat projecting, 
slightly scalloped margin, also furnished with small papillae. The gill is formed of 
seven tripinnate leaves, arranged in the shape of a large horse- shoe. The anal papilla 
(2'5 mm. high), with its slightly scalloped margin, lies behind in the opening of the 
horse-shoe, which it completely fills ; the fissure-shaped renal pore lies to the right at 
the base of the anal nipple. The outer mouth was contracted like a pore ; on either side 
of it the fold-like tentacle, furnished with a longitudinal furrow. The sides of the body 
had almost disappeared ; the contracted genital opening in the usual place. The foot 
is strong, only projecting slightly (about 2\5 mm.) from the sides of the body, and rather 
more in front (4\5 mm.) ; the anterior end rounded, with marginal furrow; the posterior 
end slightly pointed, somewhat rounded. 
The intestines do not shine through any part of the body. The peritoneum is 
colourless. 
The central nervous system is greatly flattened (fig. 1 ) ; the cerebro -pleural ganglia 
kidney-shaped, rather thicker before than behind, the two portions indistinctly separated ; 
the pedal ganglia (fig. 1, a, a) a little larger than the pleural. The common commissure 
(fig. 1 ,b) rather wide and powerful. Each proximal olfactory ganglion (fig. 1) forms a small, 
roundish, short-stalked swelling at the origin of the nervus olfactorius, the distal ganglia 
olfactoria a small oval swelling at the root of the rhinophores. The buccal ganglia 
(fig. 1, c) are rather larger than the ganglia olfactoria proximalia, longish-oval in shape, and 
connected by a short commissure ; the gastro-oesophageal ganglia are rather short- 
stalked, also longish-oval in shape, and have a single row of larger nerve-cells (fig. 1). 
1 R. Bergh, Malacolog. Untersuch. (in Semper, Reisen im Archip. cl. Philipp., Tli. II. Bd. ii.), Heft xiii., 1878, 
Tat lxiv. fig. 20 (Archidoris tuberculata). 
