82 
Mr. W. W. Stoddart, F.G.S.,read a paper on Tribolites, so called from 
their being divided into three lobes. They were among the most ancient 
forms of animal life, and had no living representatives, the nearest 
approach being the I^imulus or King-crab, common in the West Indies. 
The general structure of this Crustacean was described, and particular 
attention drawn to the hinder legs, which served the office of gills, each 
carrying on their outer edge a series of plates like the leaves of a book- 
whence the name Phyllopod, ' leaf-footed.' Except the dorsal part and the 
immoveable epistoma, the whole of the under surface of the body was 
soft and perishable, which would account in great measure for the assertion 
of some writers that Tribolites had no legs. The number of genera and 
species of Tribolites M^as very large, more than 200 species being found in 
Great Britain alone. The Agnostitlse were the lowest in organization, the 
Phacopidae the highest. Tribolites were brought into being at the earliest 
part of the Cambrian period, attained their fullest development at the 
Llandeilo and Caradoc ages of the Silurian, and died out in the upper 
Carboniferous shales. Mr Stoddart then, by the aid of diagrams, minutely 
described the parts of the Tribolile usually found, giving the palseon- 
tological terms for them. The fossil remains were formed from a chitinous 
substance, probably identical v»'ith the valves of a Lingula, or the elytra of 
beetles, and were divided into the head or carapace, divided by many kinds 
of furrows ; cheeks fixed and moveable ; the front margin of the head with 
the rostral shield and labrum or epistoma ; the thoracic rings and side 
lobes or pleurae (always anch^/losed) ; on the number and variety in which 
specific distinctions were founded ; and the pygidium or tail. The head 
afforded generally a very reliable means of determining genera. Some 
Trilobites, as the Calymenid^ and Asaphidse, had the power of rolling 
themselves up into balls — and a section of a Calymene was exhibited, in 
which it was thought that traces of phyllopod feet could be detected. The 
Olenidse and Ogygidse had not this power. A specimen of a very rare 
Trilobite, Encrinurus valeolaris, was also shown, only one other specimen, 
and that in the I5ritish Museum, being known to the speaker as having 
been hitherto found. Mr. Stoddart then briefly described the ex- 
quisitely beautiful eye of the Tribohte. It was compound, like 
those of insects — being made up of a number of prisms, and having a 
crystalline lens and pupil, but all arranged under one cornea, and termi- 
nating in the optie nerve, Mr. Barrande stated that he had ascertained 
more than 30,000 facets in each eye of Brontes palifer. Some species, 
however, did not show any fjicets, which were most developed in the- 
Phisco] id*. In the remains of earliest Tribolites, eyes were always 
absent, ^jrubably from the cheeks being moveable; but in some cases, as 
in the Anopolenus, the cheeks, eyes, and head spines, usually supposed to 
be absent, were found in an abnormal position. 
The President, in commenting upon the paper, made some appro- 
priate remarks upon these medals of creation, and upon their importance 
as iiciui^' in man} cases, peculiar to, and characteristic of, certain definite 
straiii.. 
