302 PALEOZOIC TIME DEVONIAN AGE. 



The land-plants belong to two prominent groups, — Conifers and 

 Acrogens (p. 1G6). The former are the lowest of flowering plants, 

 the latter the highest of the flowerless plants, or Cryptogams. 

 Mosses, an inferior group of Cryptogams, are unrepresented. Thus 

 the new creations commenced with neither the highest nor the 

 lowest of plants, but at an intermediate point in the series, where 

 the lower and higher groups come together. There was neither 

 moss nor grass ; and no showy flowers existed to contrast with the 

 verdure. The Conifers have inconspicuous flowers, and of all flower- 

 ing plants approximate most nearly in fructification to the Acrogens. 

 Moreover, between the Acrogens and the Conifers of the era there 

 was an intermediate group (although most closely related to the 

 latter), which included the Sigillarise: so that there was a remark- 

 able unity in the early botany of the world. The Acrogens repre- 

 sented belong to the Lycopodium, Equisetum, and Fern tribes. 



The Fishes of the age are also of two groups, — the Selachians, or 

 Sharks, and the Ganoids. The earliest species, therefore, instead of 

 being the lowest of fishes, belong to the highest of the three grand 

 divisions : moreover, instead of being small, some of them were 

 twenty or thirty feet long. The Selachians are highest among 

 fishes even in modern seas. 



These early fishes — especially the Ganoids — have strong Reptilian 

 characteristics, as Agassiz long since observed, and they were thus 

 comprehensive types, foreshadowing the class of Reptiles afterwards 

 created. Hence, while plants began at the middle of the scale, 

 Fishes commenced at the top, — not, indeed, with the very highest 

 tribes of the groups introduced, for these belong to later time ; but 

 the groups themselves rank highest in the class of Fishes, as stated. 

 In fact, the commencement was at a point above the true level of 

 Fishes, verging towards the higher grade of Reptiles ; and it was not 

 till long afterwards that the fish-type appeared in its purity. 



Among Ganoids, the species of Pterichthys (fig. 516) have many of 

 the characters of a turtle, — its paddles and its covering of plates ; and 

 those of Coccosteus present features of some sculling reptiles. Many 

 of the other Ganoids are Sauroid, in having the teeth closely like 

 those of the early Reptiles, and a joint made of concave and convex 

 surfaces at the junction of the head and neck, hence admitting of 

 some motion, — a characteristic belonging to none of the common 

 osseous fishes (Teliosts). Another Reptilian characteristic is the 

 lung-like structure of the air-bladder, the organ which answers to the 

 lung in air-breathing Vertebrates. Moreover, the old Ganoids bear 

 two striking marks of antiquity: (1) they have cartilaginous skele- 

 tons, and (2) vertebrated tails. Besides, they are at the present 



