94 THE GASTROPODA 
and extensive cuticle, which is generally more fully developed near 
the origin of the intestine, and may extend into it, as in Paludina, - 
Cyclostoma, and certain Pulmonates. Sometimes this lining presents 
a specialisation in the form of a longer or shorter cuticular projec- 
tion known as the crystalline style, which may be lodged in a thick- 
walled caecum or may project as a rod into the proximal part of 
\\ 
on | > 
Fic. 75. 
Pteroceras, right-side view of the male, with the mantle laid open. a, anus; b.d, bile-duct; 
c.g, cerebral ganglion ; c7.s, crystalline style ; f.foot; g, gill; g.g, gonad ; g.o, genital orifice ; h, 
heart; hy.g, hypobranchial gland; i.g, infra-intestinal gland; im, intestine; k, kidney; m, 
mouth ; 02, oesophagus ; op, operculum ; p, penis ; pa, mantle; p.g, pedal ganglion ; pl.g, plural 
ganglion; ra, radula; 7.0, renal orifice ; 7.p, reno-pericardial orifice ; s.g, supra-intestinal gan- 
arin . . 2 y . : 7 
glion ; si, siphon; s.gr, seminal groove; st, stomach; t, tentacle. (After F. M. Woodward.) 
the intestine. This structure is found in various Docoglossa, 
temporarily at least in Misswrella, in Trochus, in numerous Hydro- 
biidae such as Bithynia, Lithoglyphus, Spekeia, Tanganyicia (Fig. 78, cr.s), 
etc., in the Melaniidae and allied forms such as Paramelania, Nas- 
sopsis, Typhlobia, etc., and in Pteroceras (Fig. 75, cr.s) among the Strom- 
bidae. In many cases the stomach is furnished with a caecum, 
generally pyloric in position and contiguous to the openings of the 
hepatic ducts. This caecum is coiled in a spiral in many Rhipido- 
