of these ganoidal fishes glittered with enamel, and was usually sculptured in the most graceful patterns or ornamented with fine lines and punctures so minute as to be almost invisible to the naked eye. Every plate, scale, fin-ray, nay, the very lips exhibited the characteristic enamel mottled over with the style of ornament peculiar to the species. And when we think we have exhausted the contemplation of these beauties, it needs but a glance through an ordinary microscope to assure us that the unassisted eye catches only a superficial glimpse of them. The more highly we magnify any portion of these old-world mummies, the more exquisite does its structure appear. In the carboniferous rocks of Great Britain, upwards of forty species of ganoids have been detected. They have a wide range in size, the smallest measuring scarce two or three inches, while the largest, to judge at least from the bones which they have left behind, must have reached a length of twenty, or perhaps even thirty feet The lesser genera (Fig. 29) were characterized by small, angular, glossy scales, usually ornamented either with a very minute punctulation, or with fine hair-like lines which sometimes exhibited the most complicated patterns. The scales were likewise occasionally serrated along the exposed edges--a style of ornament which gives no little richness to the aspect of the dermal covering. The fins, closely imbricated with small angular scales of bone, sometimes displayed a striated ray in front, but this neither possessed the strength nor the formidable aspect of the corresponding spine among the placoids. The head was encased in a set of bony plates fitting tightly into each other, and ornamented with various patterns according to the species. The teeth were very small and fine, resembling the bristles of a brush, but in at least some species intermingled with teeth of a larger size. The minute style of dentition in these smaller fishes has been thought to indicate their habit of keeping to the bottom of the water and feeding on the soft decaying substances lying there. Nowhere have I seen the small rhomboidal scales of the _palæoniscus_ so abundant as among dark shales charged with cypris cases and fragments of terrestrial plants, and on such occasions the idea has often occurred that these graceful little fishes, like the _amia_ of the American rivers, may have fed on the cyprides that swarmed along the bottom of the estuary. [Illustration: Fig. 29.--Amblypterus macropterus (a Carboniferous ganoid).]