98 THE HAMILTON ASSOCIATION. 
a French naturalist (D’Orbigny) asserts he found the young of 
a species in the River Parana, singular to relate, attached by a 
byssus—a circumstance which can hardly have escaped the 
attention of evolutionists to-day. 
Unios occur in Mesozoic rocks, as stated by Woodward. 
= THE CHAMID. 
These Molluscs are better calculated to attract the Concholo- 
gist by their singularity than beauty. The uneven surface 
ridged and furnished with rows of spiney lamellz is merely one 
of their peculiarities. Inhabiting tropical seas and found on 
coral reefs, it attaches itself by ezther valve. Woodward asserts 
if by the right, the dentition is reversed, the left having the 
single tooth. Independent of the general appearance the struc- 
ture of the shell, consisting of three layers, is noticeable. The 
fossil Dzcevas, a sub-genera of the Chamidz, has been found in 
the middle Oolite. 
TRIDACNID.E—( Clam Shells ). 
These deeply ribbed, equi-valve and ponderous shells seem 
to have put in an appearance quite recently, fossil species occur- 
ring in the Tertiaries of Egypt. The animal is attached by a 
’ 
‘“byssus ” or ‘‘ free,’ and when the weight and thickness of the 
shell are taken into consideration one finds it difficult to under- 
stand the necessity of its being furnished with the means of 
fixing itself by the byssus to reefs at all. The Tridacna Squa- 
mosa (the type of the family) is said to be sometimes a yard and 
a half long—perhaps the ‘‘ Tridacna Gigas” was meant the 
or Bears-paw Clam—differs from the 
b) 
‘* Hippopus Maculatus’ 
former in shape. This may be found almost in every collection. 
Various stages of growth may be noticed in Mrs. Carey’s case. 
The ‘‘ Tridacna Gigas,” unrepresented there, is rather expen- 
Notr.—Fossil Unios have been found in Irish fresh water Devonian 
the equivalents of Hugh Millar’s old red sandstone. Prof. Forbes 
named one found in Kilkenny, Anodonta Jukesu. Woodward was 
unaware of this discovery, for he credits the Weald with the oldest 
fossil Unio. The late acting Palzontologist of the Irish survey, Prof. 
W. H. Bailey, F.L.S., F.C.S., forwarded the figure of the shell now 
submitted for your examination. 
