EEPORT ON THE NUDIBR ANCHI ATA . 
137 
separated by a smooth, narrow space from the stomach folds ; these folds could be traced 
as far as the anal papilla (PL V. fig. 2). — The alimentary canal contained a quantity of 
whitish, rather hard matter, which was less abundant in the oesophagus and intestine ; it 
consisted of calcareous matter and numerous littoral Algte, 1 2 among which were species of 
Calothrix and Percursaria (Enteromorpha) percursa, Ag., mixed with the debris of a 
species of Cladophora } 
Of the three divisions of the liver, which were all of a dark greenish-grey colour, the 
anterior (PL Y. fig. 27, f) was 16'5 mm. broad by 9 mm. in breadth and 10 mm. in height ; 
its shape was concavo-convex, and it was traversed on its upper surface from the right margin 
by three deep furrows, reaching almost to the middle, and dividing it into four portions ; 
further it was divided into lobes by numerous smaller superficial furrows ; the intestine 
occupied a furrow on its upper surface ; the anterior liver opens into the first stomach 
(Pl. VI. figs. 6, c, 7, c ), to the left of and above the cardia. The lower and smallest liver 
mass, lying beneath the anterior stomach (Pl. YI. fig. 7,d ), was only 13 '5 mm. in length, 
by 14 mm. in breadth and 4'5 mm. in height; it is somewhat flattened in form, and 
traversed by superficial furrows, and opens by a short bile duct below the cardia into the 
anterior stomach (fig. 6, d). Finally the hindermost and largest liver, divided from the 
anterior by the masticatory stomach, has a length of 22 mm., a breadth of 15 mm., 
and a height of 8 mm. (Pl. Y. fig. 27, g ; Pl. VI. fig. 7,g) ; from the left margin two 
furrows run into the middle, and so divide the liver into three lobes ; it opens into the 
recess behind the masticatory stomach (Pl. YI. figs. 6, g, 8, b). The bile ducts are short but 
wide; the undermost is the shortest (fig. 6,d); the hindermost is the longest (fig. 6,g, 8, be), 
and is divided into three or four branches, which are again subdivided, and can be 
followed into the smallest lobes. On the main bile ducts were here and there smaller and 
larger liver lobes (Pl. VI. fig. 10); the walls of the chief bile ducts are strong and 
muscular, the inside provided with longitudinal folds with a thick epithelium. 
The inner wall of the pericardium (PL Y. fig. 27) is thinner in front than behind, where 
it passes directly into the walls of the lung cavity ; the outer wall of the pericardium is 
thinner. The contracted yellowish-white ventricle of the heart was (flattened and) pear- 
shaped, about 7' 5 mm. long; the atrium generally 12 mm. long; the atrio-ventricular 
valves (Pl. YI. fig. 1 1, a) are crescentic, with numerous thin habense musculares ; the aortic 
valves were also conspicuous. The truncus aortce (within the pericardium) (Pl. Y. fig. 27) 
is strong, and is prolonged in front along the right side wall of the body, and there gives 
1 These species were determined by help of the Algologist, Kolderup-Rosenvinge. 
2 In Onchidium pedaense, S., I found the contents of the digestive tract to be calcareous matter and sand, 
among which were many Polythalamia, and this seems generally to be the case in Onchidium. Cf. Semper, Einige 
Bemerkungen iiber die Nephropneusten v. Jherings, Arb. aus dem Zool. Zoot. Inst, in Wurzburg, Bd. iii., 1877, p. 484, 
Note 1 (“Sie fressen wie die TIolothurien nur Meeressand ”). According to Joyeux Laffuie ( loc . cit., p. 14), the 
Onchidium celiicum appears to live upon Algse, especially Ulvse, but it swallows a small cjuantity of sand to aid it in 
mastication. 
(zool. chall. exp. — part xxvi. — 1884.) 
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