134 CLASS III. GASTEROPODA. ORDER VII. PECTINIBRANCHIATA. 
did Cuvier ; but when the anatomy of these animals was finally examined 
by De Blainville, their affinity with the Neritinze became manifest, con- 
firming as accurately as possible the propriety of Lamarck’s arrange- 
ment. The Navicellz differ from the Crepidule in being fluviatile ; they 
differ also in being furnished with an operculum ; they do not become 
attached to other bodies ; nor do they exhibit any irregularity of growth. 
The same regularity, which always marks the growth of the shell, is im- 
parted to the septiform columella, and in all these several particulars 
they entirely agree with the Neritine. 
Until within the last few months only five species of Navicellz were 
known ; ten new ones have been recently described by M. Recluz, and 
we have two or three more still to come from the inexhaustible stores of 
Mr. Cuming. 
The shell of Navicella may be described as being transversely elliptic, 
or oblong, patellaform, convex superiorly, and covered with an olivaceous 
epidermis ; it has no spire; the vertex is obliquely inflected at the mar- 
gin, and the lip is entire and flattish, forming superiorly a very thin, 
septiform columella; the aperture is very large, and distinctly marked 
with two muscular impressions, one on each side. The operculum is tes- 
taceous, and nearly square ; it is solid, flat, and has a sharp lateral pro- 
jection. 
Examples. 
PI. CXCIX: Fig. 1. 
NavIcELLa TESSELLATA, Lamarck, Anim. sans vert., new edit., vol. viii. 
p. 564. Encyclopédie Méthodique, pl. 456. f.3.a,6. Recluz, Re- 
vue Zoologique Soc. Cuv., 1841, p. 380. 
Pl. CXCIX. Fig. 2 and 3. 
NavicELLa LineatTa, Lamarck, Anim. sans.vert., new edit., vol. viii. 
p. 564. Encyclopédie Méthodique, pl. 456. f. 2. a,b. Recluz, Re- 
vue Zoologique Soc. Cuv., 1841, p. 380. 
Septaria navicula, De Férussac. 
