96 
THE YOYAGE OF H.M.S. CHALLENGER. 
ring (PL II. fig. 2) was rather broader above (fig. 2, a), but otherwise of uniform breadth, 
interrupted in the mesial line both above and below ; above by a narrow furrow, below by 
a broad interspace (fig. 2, b). The prehensile ring is formed of perpendicular, tolerably 
thin, small (figs. 3, 4) rods, which attain a height of ‘18 mm. The tongue was large and 
broad, with a deep cleft, which was covered beyond the edge with the pale chitinous 
yellow, varying-coloured radula. In the latter there were eighteen rows of dental plates, 
and in the short, thick radula-sheath sixteen more developed rows and three imperfectly 
developed, so that their total number amounted to thirty-seven. There were the marks 
of two other rows, which had been lost, at the point of the tongue ; the first six or seven 
were incomplete, and the plates often injured. There were seventy plates (on either 
side) in the eighth row of the tongue, and seventy-three at the upper root of the tongue, 
and the number seemed hardly to increase backwards. The plates were of a pale 
yellowish colour; the height of the outermost four amounted to '075-T-T4-*16 mm.; 
the height increased to nearly ’28 mm., and then gradually diminished, till in the three 
innermost plates it only amounted to T-‘09-‘075 mm. The plates (figs. 5-9) were of the 
usual shape, with the usual wing-like development of the inner border of the body (figs. 
7, 8), with rather blunt hook. The narrow rhachis had a fine fold (fig. 5, a). The inner- 
most plates (fig. 5,b,b ) were provided with a low and thick hook, the outermost (fig. 9, a) with 
slender hook and short body. The structure of the pulp of the radula was as usual (fig. 10). 
The salivary glands (fig. 11) were yellowish-white, the anterior half much thicker (as 
much as 2 mm.) than the posterior, which is pointed towards the end. In the specimen 
examined, the posterior half was turned forwards, and the posterior end only was 
(fig. 11, b,b) bent round the large commissure. The entire length of the glands amounted 
to about 2 cm. The ducts of the salivary glands (fig. 11 , a, a) were short. 
The oesophagus (PI. I. fig. 22, a) was about 13 mm. long by from 3-2 mm. in diameter ; 
the inside showed the usual longitudinal folds. The oesophagus, which became a little 
widened behind into a sac 5 mm. long, communicating immediately with the biliary duct, 
opened into the wide stomach. The stomach itself (fig. 22, b) is nearly 13 mm. long by 12 
mm. in diameter and 8 mm. high, the greater part of it projecting freely before the liver 
(fig. 22, dd ) ; the inside has fine longitudinal folds. The intestine (fig. 22, ccc ), which sprang 
from the anterior margin of the stomach, ran down in front of the anterior end of the 
liver, lying in a furrow on the latter, rose again a little way, and then, embedded in a 
continuation of the furrow, passed on the upper surface of the liver near the right margin to 
the anal papilla. The length of the intestine when extended amounted to fully 5 cm., and 
had an almost constant diameter of 2'5 mm. The inside of the intestine was provided with 
fine longitudinal folds. The whole digestive cavity, from the buccal cavity to the anal 
papilla, was filled with food, composed of a spongy siliceous mass with long spicules, and 
enclosing small corals, little pieces of conchylia, and a small well-preserved Rissoa (?), 
4 mm. long. 
