206 BULLETIN OF THE 
searching for traces of antenna. As known at present, the Trilobite 
Calymene senaria has twenty-six pairs of appendages. 
The thoracico-abdominal appendages have been treated thus far as 
simple jointed ambulatory legs, without reference to the attached respi- 
ratory apparatus. On examining the basal joint of the leg as shown in 
several sections a short, jointed appendage is seen attached to it on the 
upper exterior side, as shown in Plate III. figs. 9 and 10, and in the res- 
toration, Plate VI. fig. 2. The finest illustration of this appendage was 
unfortunately lost in 1875 before a sketch was taken of it.* Subse- 
quently a number of sections were gradually ground away, commencing 
at the extremities of the pleuræ and working in towards the median 
lobe. First, the branchiæ and the extremities of the legs were seen, 
and then the jointed arm, which was followed up to the base of the leg. 
This manner of working enabled the observer to learn something of 
the position of the various parts, but it destroyed the evidence of what 
was observed. 
Above the small jointed appendage, or epipodite, there is attached a 
branchia extending outward and downward beyond it. 
Many perfectly preserved and beautiful specimens of Asaphus 
platycephalus have been cut into sections, but with little success in 
obtaining traces of the appendages, etc. Plate IL. fig. 9, shows the 
basal joint of a leg and another section not illustrated gives evidence 
that the legs extended out beneath the pygidium, as shown by their 
basal joints. In Acidaspis Trentonensis the legs, both cephalic and 
thoracic, have been observed, as also the spiral branchie. 
In review of our information concerning the thoracico-abdominal 
appendages, I think we are justified in stating that there is a series 
of jointed legs extending from the cephalic shield beneath the thorax 
and pygidium to the posterior segment of the latter; that, as far as 
known, they were ambulatory, and formed of six or seven joints; that 
to the basal joint there were attached an epipodite and branchia ; 
and that, from the proof we now have, there is little doubt but that 
the appendages beneath the pygidium did not vary essentially from 
those of the thoracic region. They may have terminated in a slen- 
der filament, or filaments, as but three joints have been seen in any one 
appendage. 
Illustrations are given of the supposed Trilobite’s leg discovered by 
M. Eichwald, and also of the two crustacean legs from the Hudson 
* Left on awriting-table, it was brushed to the floor, and from thence swept up and, 
thrown into the fire by a careless domestic, 
