PROGRESS OF LIFE. 597 



If, therefore, these simple species existed in the Azoic era, they were system- 

 less life, and only foreshadowed the great systems of life which Were after- 

 wards displayed according to their respective types in the true Zoic ages. 



2. Kingdoms. — (a.) Vegetable. — The earliest Land-plants included Acrogens 

 or the superior Cryptogams, and Conifers or the inferior Phaenogams; and 

 among them there were the intermediate comprehensive types of Lepidoden- 

 drids, Calamites, and Sigillarids. See p. 283. 



(6.) Animal. — Among the earliest of Animals in the Primordial there were the 

 Cystids (Crinoids). These belong to the Echinoderms, which make the upper por- 

 tion of the inferior subdivision of animals ; and they are a comprehensive type 

 between Radiates and Mollusks (the lower portion of the superior subdivision). 

 Some early kinds have almost the same absence of symmetry in the body that 

 belongs to Mollusks, and are furnished with only two arms. The associated 

 superior species were Mollusks and Articulates ; and the earliest Mollusks, the 

 Lingulas, and others among Brachiopods, stood on a stem like the Cystids, and 

 had also two arms. 



3. Sub-kixgdoms. — (a.) 'Mollusks. — The Mollusks of the earliest or Primordial 

 period were from the higher group of the inferior division, that is, the Brachio- 

 pods. The associated superior species comprised Cephalates before Acephals, — 

 that is, the middle before the inferior group. 



(b.) Vertebrates. — The earliest Vertebrates were of the inferior subdivision, 

 or that of Fishes, and from its upper portion, — that is, the orders of Ganoids 

 and Selachians. The Ganoids were a comprehensive type foreshadowing 

 the lower group of the suj)erior division of Vertebi'ates, — that is, Reptiles 

 (p. 302), which group did not make its appearance until the close of another 

 age. 



4. Classes. — (a.) Gymnosp>erms in the Vegetable kingdom. — The group of Cy- 

 cads is one of the most marked of comprehensive types, as explained on 

 page 418. 



(b.) Crustaceans. — The earliest Crustaceans, eomniencing even in the lowest 

 Primordial, were Trilobites, ranking with the highest of Entoniostracans, or 

 the inferior subdivision, or even above their true level. They constitute a com- 

 prehensive type, foreshadowing the Tetradecapods, which are not known to 

 have appeared before the Carboniferous age (p. 375). There was also another 

 comprehensive type in the same early strata, — the Phyllopods, foreshadowing 

 the still higher division of Decapods, which appeared under the form of Macrou- 

 rans at the same time. 



(c.) Reptiles. — Among the earliest Reptiles in the Carboniferous age there 

 were the Labyrinthodonts, — the highest of the inferior division, a comprehensive 

 type having many characteristics of true Reptiles (p. 345). The associated 

 species were other Amphibians; also species of the lower groups of the 

 iuperior division, — that is, the lower Lacertians and Swimming Saurians 

 (p. 351). 



(d.) Mammals. — The earliest Mammals were Marsupials of the inferior sub- 

 division, and Insectivores of the superior; and the order of Insectivores is a 

 typical one among the lower superior. See, further, Appendix F. 



