432 PYRAMIDELLID A. 
factorily determine ; but they give the foot the appearance of 
being formed of three lobes, an anterior and two suboval 
lateral ones with rounded termini. This is the great singu- 
larity, and malacologists would constitute a genus for it, but 
in all the essential pots it is a decided and typical Chem- 
nitzia. The operculum is fixed on a plain, not extended lobe ; 
it has the flap-process or apophysis of the tribe, not m the 
same plane, but inflexed at right angles; it is cartilagmous 
and flexible in this species, and the striz of increment range 
in elliptical curves, as in the typical Chemnitzia pallida. 
The animal is not lively, at least the only one I have ex- 
amined was not so; and it is possible more active creatures, 
which are exceedingly rare, may cause some modification of 
the points described. It inhabits the littoral zone, and is 
unrecorded. Axis =, diameter ;!> uncie. 
A second example has shown, that the transverse groove in 
the foot does not exist, and that in the first specimen it was 
due to contraction, which when it is completely developed 
disappears ; nevertheless the structure is peculiar : at rest it is 
sub-oval, but divided into two portions by an apparent super- 
ficial line due to colour; when fully deployed, the anterior one 
is constricted, slender, attenuated, capable of great extension, 
slightly auricled and emarginate, subhyaline white; the poste- 
rior portion is sub-oval, short, broad, fleshy, of an opake pale 
drab, divided by a deep medial longitudinal fissure, that seems 
almost to separate the integuments into two lobes, forming 
together a rounded termination with a narrow central emar- 
gination. 
Cu. pecussata, Montagu. 
Odostomia decussata, Brit. Moll. ii. p. 303, pl. 97. f.6, 7; and iv. 
p. 281. 
Animal inhabiting a pale drab spiral decussated shell of 
4-5 volutions; it is hyaline white, except the proboscidal 
muzzle, that passes for the mentum with some malacologists, 
which is pale pink or red. The mantle is even. The rostrum 
of this species is less lobed and more truncate than in its con- 
geners, but it has at times varying phases; it is small, sub- 
