172 CLASS III. GASTEROPODA. ORDER VII. PECTINIBRANCHIATA. 
tunda, marginibus disjunctis, labro acuto, sinu interdum leviter emar- 
ginato. 
We have now to consider a genus of mollusks, which Lamarck sepa- 
rated from the Linnean Turbines on account of the great length to which 
their shell is extended by its multiplicity of volutions. Commencing 
from a point, it gradually enlarges to six or seven inches in length, whilst 
the diameter at the broadest part is under one inch. The Turritelle are 
very closely allied to the Turbines, but have nevertheless been somewhat 
removed from them by De Blainville, in placing them between the Del- 
phinule and the Scalarie. If it were not that the margins of the aperture 
in the shell of Turritella were disjoined in such a manner as to exhibit a 
distinct columella, we might certainly appreciate this arrangement: in 
both those genera the margins of the aperture are continuous, and the 
volutions of the shell are so independent of each other as not to allow 
of the formation of a columella; they cannot, therefore, be well admitted 
in such close affinity, though undoubtedly belonging to one and the same 
family. 
The shell of Turritella may be described as being turrited, very long, 
and narrow, composed of a number of whorls closely rolled into a sharp- 
pointed spire, forming at the aperture in all stages of growth a smooth, 
curved columella; the aperture is nearly round, with the margins dis- 
joined ; and the lip is simple, acute, and sometimes slightly emarginated 
with a sinus. , 
Examples. 
Pl. CCXXIV. Fig. 1. 
TURRITELLA DupPLIcaTA, Lamarck, Anim. sans vert., vol. vii. p. 56. En- 
cyclopédie Méthodique, pl. 449. f. 1. a, 6. 
Turbo duplicatus, Linnzeus. 
Pl. CCXXIV. Fig. 2. (fossil.) 
TuRRITELLA suLcATA, Lamarck, Anim. sans vert. Supp., vol. vii. p. 561. 
