Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . marine worms, surrounded by asolid sheath. The class of insects is entirely wanting. § 666. The inferiority of the earliest inhabitants of ourearth appears most striking among the vertebrata. Thereare as yet neither birds nor mammals. The fishes, and a fewreptiles whose fossil foot-marks we only know, are the solerepresentatives of this division of animals. § 667. The fishes of that early period were not likeours. Some of them had the mos
Outlines of comparative physiology touching the structure and development of the races of animals, living and extinct : for the use of schools and colleges . marine worms, surrounded by asolid sheath. The class of insects is entirely wanting. § 666. The inferiority of the earliest inhabitants of ourearth appears most striking among the vertebrata. Thereare as yet neither birds nor mammals. The fishes, and a fewreptiles whose fossil foot-marks we only know, are the solerepresentatives of this division of animals. § 667. The fishes of that early period were not likeours. Some of them had the most extraordinary forms, sotha-; they have been often mistaken for quite different animals ;for example, the Pterichthys (fig. 3/9), with its two winglikeappendages, and also the Coccosteus (fig. 380), of the samedeposit, with its large plates covering the head and the ante-rior part of the body. There are also found remains of sharksspines, as well as palatal bones, the latter of a very peculiar 400 GEOLOGICAL SUCCESSION OF ANIMALS. kind. Even those fishes which have a more regular shape,as the Dipterus, have not horny scales like our common fishes,. Fig. 379.—Pterichthys, from the Devonian rocks of Scotland.—Agass. but are protected by a coat of bony plates, covered withenamel, like the gar pikes (Lepidosteus) of the Americanrivers. Moreover they all exhibit certain characteristic fea-tures, which are very interesting in a physiological point ofview. They all have a broad head, and a tail terminating intwo unequal lobes. What is still more curious, the bestpreserved specimens show no indications of the bodies of thevertebrae, but merely the spinous processes ; from which it mustbe inferred that the body of the vertebra was cartilaginous, asit is in our sturgeons. § 66^. Recurring to what has been stated on that point inChapter Twelfth, we thence conclude that these ancient fisheswere not so fully developed as most of our fishes, being, like AGES OF NATURE. 401 the sturge
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectzoology, bookyear1870
