3.96 l-’OSSIL EYES OE TRILOBITES. 
the living Branchipus, nor should the primeval 
form of Limulus have possessed such an inter- 
mediate character, or have remained unadvanced 
in the scale of organization, from its first appear- 
ance in the Carboniferous Series,* through the 
midway periods of the secondary formations, unto 
the present hour. 
Eyes of Trilobites. 
Besides the above analogies between the Tri- 
lobites and certain forms of living Crustaceans, 
there remains a still more important point of 
resemblance in the structure of their eyes. This 
point deserves peculiar consideration, as it af- 
fords the most ancient, and almost the only 
* The very rare fossil engraved in Martin’s Petrifacata Derbi- 
ensia (Tab. 45, Fig. 4,) by the name of Entomolithus Monocu- 
lites (Lunatus) appears to be a Limulus. It was found in Iron 
Stone of the Coal formation on the borders of Derbyshire. 
A similar fossil in the collection of Mr. Anstice, of Madely, is 
engraved in our Plate 46", Fig. 3. 
In the Secondary period, during the deposition of the Jurassic 
limestone, the Limulus abounded in the seas which then covered 
central Germany ; and it still maintains its primeval interme- 
diate form in the King Crab of the present ocean. 
My friend Mr. Stokes has discovered, on the under side of 
a fossil Trilobite from Lake Huron (PI. 45, Fig. 12.), a crus- 
taceous plate (f.) forming the entrance into the stomach, the 
shape and structure of which resemble those of the analogous 
parts in some recent Crabs. This organ forms another link ol 
connexion between the Trilobite and living Crustaceans. — GcoL 
Trans. N. S. vol. i. p. 208, Pi. 27. 
