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LETTER XV. 
VULSELLA MALLEUS AVICULA PERNA CRENATULA 
PLACUNA HARPAX PECTEN......LIMA PEDUM PANDORA 
CORBULA ANOMIA CRANIA TEREBRATULA CALCEOLA 
HYALiEA ORBICULA LINGULA BALANUS TUBIC1NELLA 
CORONULA ANATIFA. 
CXXXVIII. Vulsella. A free, longitudinal, nearly equivalved 
shell, with a flattish callous hinge, without teeth, projecting alike on 
each valve ; and a conical rounded pit for the ligament, terminating 
in a very short bent beak. 
This genus is formed by Lamarck for the reception of My a vulsella, 
Linn ; Vulsella lingulata, Lam. Humph. Mus. Tab. 46, Fig. a. It 
is not, I believe, known fossil. 
CXXXIX. Malleus. A free shell, a little gaping near the beaks, 
fixing itself by a byssus, and having its valves of the same size. The 
hinge without a tooth, rather projecting, and supplied with a pit for 
the cartilage, placed obliquely on the edge of each valve, and separated 
by the opening which gives a passage for the byssus. 
I am not certain of this shell having been found fossil, although, I 
think, I have seen impressions of it in lime-stone. 
CXL. Avicula. A free shell, a little gaping near the beaks, fixing 
itself by a byssus, and having its valves of unequal size ; the hinge 
without a tooth, and rather callous. The cartilaginal pit oblong, 
marginal, and parallel to the edge by which it is sustained. 
