26 
Umbrella. — Shell external, orbicular, sub-irregular, nearly flat, slightly convex above, 
white, with a small apex near the middle; margin acute, internal surface rather 
concave, having a callous disk, coloured, depressed in the centre, surrounded by 
a smooth border. 
Plate XIII. Fig. 15, 16. U. Indica. (Patella umbellata.— Gmel.) 
CALYPTRACIANA 7 Genera. 
Shell always external, covering the animal. 
Parmophorus. — Shell oblong, subparallelipipedal, slightly convex above, obtuse at the 
extremities, anteriorly channelled by a slight sinus, and having, towards the pos- 
terior part, a small pointed apex, inclined backwards ; the lower surface slightly 
concave. 
Plate XIV. Fig. 1. P. australis. (Patella ambigua. — Chem.) 
(a) Under side of ditto. 
Emarginula. — Shell shield-like, conical; summit inclined ; the cavity simple, having a 
notch or hollow cut on its posterior margin. 
Plate XIV. Fig. 2. E. rubra. 
Fissurella. — Shell shield-like or depressed conical, concave below, perforated at the 
summit ; without any spire ; the perforation oval or oblong. 
Plate XIV. Fig. 3. F. pustula. (Patella pustula. — Chem.) 
Pileopsis. — Shell univalve, obliquely conical, anteriorly recurved; apex bent, almost spi- 
ral; aperture rounded-elliptical; the anterior margin shortest, acute, slightly si- 
nuated, the posterior largest and rounded : one elongated, arched, transverse mus- 
cular impression, situated under the posterior margin. 
Plate XIV. Fig 4. P. ungarica. (Patella ungarica.— Linn.) 
Calyptr^a. — Shell conoidal, summit vertical, imperforate, subacute; base orbicular: 
the cavity furnished with a convolute lamina, or a spiral diaphragm. 
Plate XIV. Fig. 5. C. equestris. (Patella equestris. — Linn.) 
(a) Under side of ditto. 
Crepidula. — Shell ovate or oblong ; the back almost always convex ; concave under- 
neath ; the spire very much inclined towards the margin : the aperture partly 
closed by a horizontal lamina. 
Plate XIV. Fig. 6 (a). C. fornicata. (Idem. — Linn.) 
(h). Under side of ditto. 
Ancylus. — Shell thin, obliquely conical, the summit pointed, inclined backwards ; aper- 
ture oval ; the margin very simple. 
Plate XIV. Fig. 7- A. fluviatilis. (Patella fluviatilis.—Gmel.) 
