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ROYAL SOCIETY OF CANADA 



lar skeletons they wei'c not easily recoi^nizeil, except in a brii^ht li<:;lit 

 and on the moistened surlaces of the shale. In that and subsequent years 

 I undertook detailed collec'tin<>: in these beds. The thin productive lay- 

 ers heiuif inclosed in ledges of compact shale, much material had to be 

 quarried awaj' in order to obtain access to them, and the work could be 

 carried on only at low tide. The best method of proceeding was found to 

 be to trace the fossiliferous layers along the ledges, and having quarried 

 out as ge slabs as possible, to convey these to where they could be 

 split up and examined at leisure. By pursuing this method sufficient 

 quantities ol' material conld be obtained to enable satisfactory compari- 

 sons to be made. The method, in short, was the same which 1 have pur- 

 sued in collecting delicate fossil plants and the smaller animal remains 

 from the Devonian and Coal formation, and which has enabled .so many 

 species of delicate vegetable organisms from Gasp^ and Nova Scotia to 

 be restoi'cd in their external forms. 



The facts observed up to 18.S0 were detailed in the ]»aper of that 

 date, in pre[)aring which I was indebted to Dr. (i. .1. Jlinde, F.R.S., the 

 author of the British Museum Catalogue of fossil sponges, ana of so many 

 valuable ])apers on these organisms, for most imi)ortant information as to 

 the structure and ))robable affinities of the s[)ecies. In addition to the 

 notes of Dr. Hinde given in the previous jiaper. I am indebted to him fo.- 

 further important suggestions contained in these i>ages, and for the 

 description of an additional .species. 



Since 1889 excavations havo been continued from time to time, with 

 the view r.ore partAularly of discovering new species and of obtaining 

 more |)erfect examples of those previously known. In noticing the results 

 obtained, I shall tii-st refer to certain points relating to mode of occurrence 

 which have been more definitely settled, and shall then present a catalogue 

 of the species, with short descriptions and figures. 



In regard to the figures. I ma\' explain that those in the text are of 

 two kinds: (1) Camera tracings, slightly enlarged, of the picules, as 

 seen under the microscope; (2) Restoraticms, mostly based on combining 

 several more or less comjtleto specimens. Those in the plates are produced 

 from enlarged photographs taken usually from moistened surfaces under 

 a bright light. The.se were printed and carefully retouched to render 

 them more distinct, then ivproduced in negatives of or near to the natural 

 size, and copied from these for printing. Those which were sufficiently 

 distinct for this, were reproduced without being touched. 



In the former ])aper, of 1SH9, Dr. Hinde ably discussed at some 

 length the state of preservation of the s})ecimens. He remarks that the 

 skeletons of the greater number of the species were ma''e up of delicate 

 spicules, often cruciform, and arranged in such a manner as to form a 

 thin lattice-like framework inclo.sing a hollow s)tace or sack, and siipjjort- 

 ing the soft animal membranes. In the meshes of this framework, and 





