24 A POPULAR EXPOSITION OF THE 
the rocks of all intervening periods. The shell is involute, the septa 
simple and mostly central in position. Our Canadian examples are 
scarce, and have not yet been thoroughly determined. 
Goniatites.—This genus first appears in Devonian strata, and be- 
comes extinct in the Triassic deposits. It belongs, as already stated 
in our introductory remarks, to the family of the Ammonitide, and is 
essentially characterized by its angulated strata (see fig. 126, above). 
The shell is involute in form, like that of the nautilus, and the 
siphuncle external and of small size. Several species occur in the 
Devonian rocks of Western Canada, but the relations of these have not 
yet been fully worked out. 
As already explained on a preceding page, the second or Dibranchiate 
Order of Cephalopods—comprising the Argonaut, the Octopus or 
* Poulpe” of the French, the Loligo, (more familiarly known as the 
Calamary or Squid), the Sepia or Cuttle-Fish, the extinct Belemnite, 
and other kindred genera—are without representatives in rocks of 
Canadian occurrence. 
Articulated Animals—The forms of the sub-kingdon Articulata 
(see vol. vi., p. 5,) are arranged in the following classes :—ANNELIDA, 
CrrrHopopa, Crustacea, ARACHNIDA, Myriapopa, and Insecta; 
but of these, the annelids, cirrhopods, and crustaceans are alone repre- 
sented by fossil examples in Canadian rocks. 
ANNELIDA.—The annelids comprise various worm-like forms, and 
are usually grouped in three Orders :—Abranchiata, Dorsibranchiata, 
and Cephalobranchiata. The abranchiate annelids are without any 
visible or external branchie. They include the common earth-worms 
and other forms unrepresented in the fossil state. The dorsibranchiate 
annelids are marine worms with tufts of branchize in the form of 
delieate filaments at regular distances along the sides of the body. 
They offer a few fossil species, but have not been recognized in 
Canadian rocks. Finally, the cephalobranchiate annelids, also marine 
types, possess thread-like branchize around the mouth or head. Some 
of these forms secrete a calcareous tube or shell for the protection of 
the worm-like body. These constitute the genera Serpula and Spir- 
orbis: the former having an irregular wavy tube, whilst in the latter 
the tube is spirally rolled up. These tubes are mostly attached to 
the backs of shells or other sub-marine bodies. A fine species of 
serpula, D. splendens, seven or eight inches in length, and a quarter 
