206 BULLETIN OF THE 



searching for traces of antennae. As known at present, the Trilobite 

 Cahjinene 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- 

 rator}'^ 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 pleurje and working in towards the median 

 lobe. First, the branchiae 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 II. fig, 9, shows the 

 basal joint of a leg and another section not illustrated gives evidence 

 that the legs extended out beneath the pj-^gidium, as shown by their 

 basal joints. In Acidaspis Trentonensis the legs, both cephalic and 

 thoracic, have been observed, as also the spiral branchiae. 



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-taLle, it was brushed to the floor, and from thence swept up and 

 thrown into the fire by a careless domestic. 



