98 ROYAL SOCIETY OF CANADA 



lar skeletons they were not easily recognized, except in a bright light 

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

 I undertook detailed collecting in these beds. The thin productive lay- 

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

 quarried away 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 layei"s along the ledges, and having quarried 

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

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

 quantities of matei-ial could be obtained to enable satisfactory compari- 

 sonj^ 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 restored in their external forms. 



The facts obseiwed up to 1889 were detailed in the paper of that 

 date, in preparing which I was indebted to Dr, G. J. Hinde, F.R.S., the 

 author of the Bi-itish Museum Catalogue of fossil sponges, and of so many 

 valuable papers on these organisms, for most important information as to 

 the structure and probable affinities of the speci.es. In addition to the 

 notes of Dr. Hinde given in the previous paper, I am indebted to him for 

 further important suggestions contained in these pages, and for the 

 description of an additional species. 



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

 the view more particularly of discovering new species and of obtaining 

 more perfect examples of those pi*eviously known. In noticing the results 

 obtained, I shall fii-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 may explain that those in the text are of 

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

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

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

 from enlarged photographs taken usually from moistened surfaces under 

 a bright light. These were printed and carefully retouched to render 

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

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

 distinct for this, wei"e reproduced without being touched. 



In the former paper, of 1889, Dr. Hinde ably discussed at some 

 length the state of jjreser-'ation of the specimens. He remarks that the 

 skeletons of the greater number of the s[)ecie8 were made up of delicate 

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

 thin lattice-like framework inclosing a hollow 8])ace or sack, and support- 

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



