Mr. S. Stutchbury on two new genera of Mollusca. 95 
these have already been so accurately described by other observers that 
it is unnecessary further to notice them. 
_ L would suggest to the Zoological Society a careful dissection of the 
right arm, as it appeared to us, upon the hurried examination made of 
the left arm of the animal, that it possesses a sterno-hwmeral muscle not 
to be found in man. The pectoro-laryngeal sacs and this muscle were 
the only striking instances of departure from the human model which we 
observed. The muscle in question appeared to rise fleshy from the 
upper part of the sternum, proceeding in a straight line to be inserted 
into the humerus upon its external surface, and a little below the neck of 
the bone. Its action would seem to be, to roll the humerus, and to 
bring the arms across the body, thus helping the animal to take hold in 
climbing, &c. 
J. GRANT. 
Calcutta, March 1829. 
Arr. XX. On two new Genera of Testaceous Mollusca, 
and five new Species of the Genus Anatina, lately dis- 
covered at Port Jackson, New South Wales ; in a Letter 
Jrom Mr. Samvuxt Sturcasury, A.L.S. 
TO THE CONDUCTORS OF THE ZOOLOGICAL JOURNAL. 
Gentlemen, 
Amonc a parcel of shells just received from Port Jackson, New South 
Wales, two, which appear to have been hitherto undescribed, have 
particularly interested me. ‘Their peculiar characters prevent their 
admission into any of the genera yet known, without giving greater lati- 
tude to established limits than would, I think, be consistent with the true 
interests of science. Although they both possess an internal testaceous 
appendage to the hinge, characteristic of the shells placed by Lamarck 
in his genus Anatina, (though not mentioned by him,) it will surely be 
allowed that the habits and economy of an animal having the power of 
locomotion must differ so widely from those which have not, that the 
