1864.] NATURAL HISTORY SOCIETY. 371 



the head, a considerable distance from its apex. From this circum- 

 stance Burmeister infers that " they swam in an inverted position, 

 the belly upwards and the back downwards," as the mouth is 

 situated so far backwards on the under side. But although even 

 the eyes of these curious creatures are often preserved, no traces 

 of the legs have hitherto been detected. It was supposed that they 

 were thin and foliaceous, for it was plausibly urged that if these 

 animals had the stout, calcareous legs of ordinary crabs, some trace 

 of them would have been met with in the rocks. 



Mr. Billings exhibited a specimen from the Trenton limestone 

 of Ottawa, which had been in part carefully extricated from the 

 matrix. He stated that in his opinion trilobites had a pair of thin, 

 foliaceous legs to each segment of the thorax, or rather abdomen. 

 The specimen of Asaphus Plafi/cej>hahis which he passed round 

 for examination was a specimen with eight thoracic segments, and 

 exhibited on the under side eight semicylindrical ridges on each 

 side of the median line, all curving outwards and forwards. 

 These he believed to be the bases of the attachment of eight pairs 

 of swimming feet — one pair for each segment of the thorax. 

 Burmeister had made a sketch of what he supposed the legs of a 

 trilobite would be like, and Mr. Billings stated that this ideal res- 

 toration was fully borne out by his specimen, except that in Bur- 

 meister's drawing the legs were directed backwards, whilst those of 

 the actual specimen pointed forwards. 



Dr. Dawson remarked that the Natural History Society might 

 well feel proud that this important discovery in palaeontology had 

 been made by one of its own members. 



Mr. Billings said that in his opinion the specimen exhibited 

 tended to verify the views that Dr. Dawson advocated with respect 

 to the Grenville fossil previously treated of. 



Mr. D. R. McCord, B.A., next made a communication " On 

 Canadian Ferns, their Varieties and Habitats." This paper is 

 printed in the present number. 



The Recording Secretary exhibited a collection of native ferns, 

 collected and prepared by Miss Isabella Mcintosh (of Burnside 

 House), among which were three species of peculiar interest. The 

 first was the " green spleenwort " (^Asplenium viride, Hudson), a 

 small species occurring somewhat rarely in mountainous districts 

 in England, and in various localities in Europe. It had been 

 previously detected in Gasp^, in the summer of 1863, by John 



