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- Genus TriartTHrus. Green. 
Body, slightly convex; contractile? 
Buckler ? OM, | : 
Abdomen, with three ar iuhaBoniy side lobes fongi- 
tudinal, narrow, and wedge-shaped. 
Fail, broad, rounded, without any membranaceous 
expansion. . : 
The name of this senate derived front the cir- 
cumstance, that the abdomen has but three articula- 
tions; an or ‘ganization which is ye ry peculiar. These 
fos sil animals * _ abundant i in the wees 
a multitude of hicctiions from different veatnteagel no 
vestige of the head or buckler could, on the most mi- 
; nute examination, be discovered. Whether these ani- 
mals, during their petrifaction, were so contorted or 
rolled up, as to bring the extremities of the body to-— 
gether, in such a manner as to present the posterior 
folded part only to the view; or whether the buckler — 
has been destroyed by the process of mineralization, 
‘as — frequently to happen with the saphs, we > 
are at a loss to determine. 
The animal remains whic belong to the ail 
Triarthrus, differ’so much in their form and general — 
characters from all the other tr ‘lobiees, that we perhaps | 
ought to regard them as forming another race of be- 
ngs. They are, ele more — —_— to this 
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