Mr. S. Stutclibury on two new genera of MoUnsca. 95 



these have already been so accurately described by other observers that 



it is unnecessary further to notice them. 



I 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-humeral 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. 



Aar. XX. On tico new Genera of Testaceous Mollusca, 

 and five new Species of the Genus Anatina^ lately dis- 

 covered at Port Jackson, New Sovth Whales ; in a Letter 

 from Mr. S-AMt^KL Stutchbuuy, A.L.S. 



TO THE CONDUCTORS OF THE ZOOLOGICAL JOURNAL. 



Gentlemen, 



Among a p-ircel 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 \vith 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 



