THE GASTROPODS CHYTRA AND LIMNOTROCHUS. 435 
shghbt{constriction. The supra-intestinal cord (.sp.) is consider- 
ably elongated ; from the supra-intestinal ganglion (g.sp.) arise 
two nerves, the left pallial nerve (n.p.’) and the visceral (2.v.’). 
A very fine nerve (¢.p.’) connects the left pleural ganglion with 
the pallial nerve, which it joins soon after its origin from the 
supra-intestinal. ganglion. The sub-intestinal cord (m.si.) is 
somewhat shortened. In like manner the sub-intestinal ganglion 
(g-st.) gives rise to the right pallial (x.p.”) and the right visceral 
nerve (z.v.'). A nerve connects the right pleural ganglion 
and the right pallial nerve (c¢.p.”). The visceral nerves (x.v.’, 
nv.) unite by a straight commissure at the base of the rmantle- 
cavity. The pleuro-pedal and cerebro-pedal connectives are long 
(fig. 15).. The pedal ganglia (g.pe.) each give off three nerves, 
two of which run anteriorly and one posteriorly. The otoeysts 
lie close behind the pedal ganglia; they are filled with many 
barrel-shaped otoliths (fig. 16) of various sizes. 
Radula.—The radula (PI. 39. fig. 20) has a feature which is 
also a characteristic distinctive of the radula of Hipponyx conicus 
(cf. 9. vol. i. p. 162), there being a strong pointed projection on 
the admedian tooth which overhangs the inner end of its serrated 
edge: .The lateral teeth are sharply pointed and serrated. 
Possibly this acute form of dentition indicates a carnivorous 
habit. 
Viscera—YVhe mouth is carried on a short snout, and opens 
~ into the buccal mass (PI. 39. fig. 13) (6.m.), which leads into a 
long and very slightly coiled cesophagus (@.). The stomach (s¢.) 
is two-chamnbered (Pl. 39. fig. 138 & Pl. 40. fig. 25). The anterior 
stomachic chamber contains a crystalline style (s.c.); the. 
posterior bears a small, but complete spiral cecum (ce.). The 
intestine (¢.) arises from the lower portion of the anterior 
-chamber of the stomach, and coiling twice, bends sharply forward. 
The rectum (7.) attains a considerable dimension, since its walls 
are very glandular, but it narrows suddenly before opening by 
the anus (a.), which has a circular, thickened rim. 
The “liver” (/.) occupies a great portion of the visceral mass, 
anda bile-duct opens at 0. 
The kidney (#%.) is. large, and the renal aperture (a@.7.) is far 
back in the mantle-cavity (Pl. 39. figs. 12 & 13). 
The heart (v. & aur.) (Pl. 39. fig. 13) is of the ordinary 
Monotoeardian' type. . The gili (Pl. 39. fig. 13, 9.) extends 
througheut: the mantle-cavity, and consists (Pl. 38. fig. 10) 
; 31* 
