On one of the specimens collected by Messrs. Hartt and Matthew, and placed by them in my hands, is a spiral form which in every particular of external marking resembles a genus of modern West Indian Land-snails.[43] I have hesitated to describe it, as the structure is lost and the form imperfect; but I cannot help regarding it as an indication that this group of land animals also will be traced back to the Devonian age. Ascending from the Devonian to the Carboniferous, we at once find ourselves in the midst of air-breathers of various types. Here are Myriapods, insects of several orders, Spiders, Scorpions, Land-snails, and Batrachian reptiles, and these of many species, and found in many localities widely separated. We can thus people those dark, luxuriant forests, to which we owe our most valuable beds of coal, with many forms of life; and as most of these belong to tribes likely to multiply abundantly where food was plentiful, we can imagine multitudes of Snails and Millepedes feeding on succulent or decaying vegetable matter, swarms of insects flitting through the air in the sunnier spots, while their larvæ luxuriated in decaying masses of leaves or wood, or peopled the pools and streams. In like manner, in imagination we can render these old woods vocal with the trill of crickets and with the piping or booming of smaller and larger Batrachians. Let us now, in accordance with our plan, inquire as to the nature of these early air-breathers and the fortunes of their families in the geological history. [Illustration: FIG. 124.—Land-snail (_Pupa vetusta_, Dawson). From the Coal-formation. _a_, Natural size. _b_, Magnified. _c_, Apex. _d_, Sculpture. Enlarged.] [Illustration: FIG. 125.—Land-snail (_Zonites (Conulus) priscus_, Carpenter). From the Coal-formation. _a_, Shell. Enlarged; the line below shows the natural size. _b_, Sculpture. Enlarged.]