APPENDIX. 
485 
DESCRIPTION 
OF 
TWO NEW INVERTEBRATED ANIMALS 
FROM AUSTRALIA, 
BY J. E. GRAY, ESQ., F.R.S. 
Lamarck separated the mother-of-pearls shell (Mar- 
garita) from the swallow-tail muscles ( Avicula ) on account 
of its more orbicular shape. Other Conchologists have 
been inclined to unite them, as some of the species of 
Avicula approach to the shape of the other genus. The 
new one just received from Australia, which I am now 
about to describe, in this respect more resembles the 
Margarita than any before noticed ; yet I am inclined to 
think that the pearl-shells deserved to be kept separate, 
as the cardinal teeth are quite obliterated in the adult 
shells, which is not the case with any Avicula! I am 
acquainted with ; and the young pearl-shells are furnished 
with a broad serrated distant leafy fringe, while the 
Avicula! are only covered with very closely applied short 
concentric slightly raised minutely denticulated lamina, 
forming an epidermal coat on the surface, 
1 . Avicula lata, pi. 6.f. 1 . 
Shell dark brown ; half ovate ; broad obliquely truncated, 
and scarcely notched behind ; covered with close regular 
very thin denticulated concentric lamina, forming a paler 
external coat. The front ear rather produced, with a 
2*2 
