100 ROYAL SOCIETY OF CANADA 



all, or nearly all. tiieso tbssilfs lioloni-- — has boon vastly increased \ty tho 

 work of Prof. F. K. Sehulze, of Berlin, on tho he.xaetinelled spoiiires 

 dre(lfi:e(l up l)y the Ciiall'.'na;er Expedition, and thus we are now hotter 

 enalded than hitherto to eonipari' the fossil and the reeent forms.' 



Tho conditions of aeeunuilation of the Metis shales seem to have 

 been very favoui-ahle to the i)vritization of ori^anie remains. The shells 

 of Linnurssonia. snuvll fraujments of Trilohitosand fronds of Alga*, seem, all 

 alike, to have been anienahle to this ehani>-e. and eyiinders and spirals of 

 solid erystalline ])yrite oeeu])y the hurrows of worms, while nodules of 

 the mineral destitute of any oru;anie form also oeeur. On tho other hand, 

 in some layers containini!; fossils, there i's no trace of pyrito, but in these 

 it is veiy difficult to see the spicules, owini;- to their similarity in colour 

 and lustre to the slate. 



v.— Notices of the Skveral Species. 



The arrangement of Pahvozoic fossil sponges is still to some extent 

 provisional. That adopted below is the one most current at present, and 

 necessarily depends entirely on the material and structure of the skeleton. 



Viewed in this way, the whole of our Metis sponges, if we except a 

 few uncertain forms to be mentioned in the sequel, belong to the order 

 Silicea, including those which form their skeleton of siliceous needles or 

 spicules. Under this are sponges with sim])le spicules (Monactinellids), 

 and these seem to be the oldest of all, since tho needles found in the 

 H'lroniau cherts and those recognized by Mr. Matthew in the Laurentian 

 appear to be mostly of this type. Others (Hexactinellids) present cruci- 

 form spicules, or s|)ieules with six rays, placed at right angles to e.ich 

 other. These are arrai\god so that the vays arc joined by their points, 

 forming very comjilex and beautiful fra'neworks. the variety of which 

 is increased by the fact that the ditterent rays may be unequally de- 

 veloped, or some of them may be abortive, giving forms available for 

 a great many beautiful constructive uses. We shall tind that the com- 

 plexity and diversity attainable b.y spicular forms, all l)ased upon one 

 general law, hut admitting of countless difl^'erences and modifications, had 

 already nearly TOached its nuiximum in a very early geological period. 



Tho Hoxactiiiellids may again be divided into two groups, according 

 to the united or loose condition of the spicules. When those are firmlj^ 

 cemented together by siliceous matter, we have the group Dictyonina^ 

 and when they are united merely by aidmal matter, and consequently 

 fall asunder on decay, they belong to the group Lyssakina. Under those 

 we have families, genera and species. 



The following list is a revision, with important additions, of that 

 given in 1889. 



