MINERALS AND GEOLOGY OF CANADA. 505 
siliceous marls and tripolis are almost entirely made up of the 
remains of these creatures. Beds of tripoli occur at Laval and 
Lanoraie (Sir W. E. Logan) in the Lower Province, but their infusorial 
forms do not seem to have been specially examined. 
Sronces.—Modern sponges consist of a gelatinous mass, full of 
pores, and possessing in general the Bae of secreting a horny frame- 
work or kind of skeleton—the “sponge” of commerce. This horny 
framework is commonly strengthened by a number of sharp spines or 
spicula, crossing each other in various directions. The spicula are 
either siliceous or calcareous, according to the species. Fossil spicula 
often oceur in flints and in infusorial deposits. Dr. Dawson has also 
detected them in the Drift deposits of Montreal, (see Part V.) The 
ancient sponges appear to have secreted a hard calcareous framework, 
and to have been more nearly related to corals. If we except the 
doubtful Stromatopora or Stromatocerium, (see under “corals,” further 
on) our Canadian rocks do not appear to have yielded any determinate 
forms. 
Ruizorops (or Le een animals of this class are 
aquatic, and, with few exceptions, of extremely minute size. They 
swarm in many of our seas. Their soft gelatinous body is sometimes 
naked, or enclosed in a horny capsule; but more commonly it is 
protected by a calcareous and usually many-chambered shell, perforated 
for the passage of long and delicate filaments, whence the name of 
the class, from piéa, a root. The latter forms, or those possessing 
shells, are generally known as Foraminifera. The only representatives 
of these in Canadian Deposits occur in the Drift or Post-Pliocene 
accumulations of Montreal and its vicinity, where they were discovered 
by Professor Dawson. (See illustrations and 
descriptions in the Canadian Naturalist, vols. 
2 and 4.) All have been recognised as identical 
with existing forms. Fig 66 is a greatly enlarged 
view of the most common species, Polystomella Fig. 66. 
umbilicatula. 
Radiated Animals.—The following Classes belong to this division : 
Poxyrirera or Corats, ACALEPHA, and ECHINODERMATA. 
Corats.—The fossil forms of Canadian occurrence referred to this 
class may be conveniently arranged in two groups: Graptolites and 
Corals proper. The true position of the graptolites, however, is 
exceedingly uncertain; but the general opinion allots them a place 
