456 ANTIQUITY OF THE [Ch. XXII. 



that, like guano, they are the droppings of birds rather than of 

 reptiles. 



Some of the quadrupedal footprints which accompany those of birds 

 are analogous to European Cheirotheria, and with a similar dispropor- 

 tion between the hind and fore feet. Others resemble that remarkable 

 reptile, the Rhynchosaurus of the English Trias, a creature having some 

 relation in its osteology both to chelonians and birds. Other imprints, 

 again, are like those of turtles. 



Mr. Darwin, in his " Journal of a Voyage in the Beagle," informs us 

 that the " South American ostriches, although they live on vegetable 

 matter, such as roots and grass, are repeatedly seen at Bahia Blanca 

 (lat. 39° S.), on the coast of Buenos Ayres, coming down at low water 

 to the extensive mud-banks which are then dry, for the sake, as the 

 Guachos say, of feeding on small fish." They readily take to the water, 

 and have been seen at the Bay of San Bias, and at Port Valdez, in 

 Patagonia, swimming from island to island.* It is therefore evident, 

 that in .our times a South American mud-bank might be trodden 

 simultaneously by ostriches, alligators, tortoises, and frogs ; and the 

 impressions left, in the nineteenth century, by the feet of these various 

 tribes of animals, would not differ from each other more entirely than 

 do those attributed to birds, saurians, chelonians, and batrachians in 

 the rocks of the Connecticut. 



To determine the exact age of the red sandstone and shale contain- 

 ing these ancient footprints in the United States, is not possible at 

 present. No fossil shells have yet been found in the deposit, nor plants 

 in a determinable state. The fossil fish are numerous and very perfect ; 

 but they are of a peculiar type, which was originally referred to the 

 genus Palceoniscus, but has since, with propriety, been ascribed, by 

 Sir Philip Egerton, to a new genus. To this he has given the name 

 of Ischypterus, from the great size and strength of the fulcral rays of 

 the dorsal fin (from loxvg, strength, and Trrepbi, a fin). They differ 

 from Palceoniscus, as Mr. Redfield first pointed out, by having the 

 vertebral column prolonged to a more limited extent into the upper 

 lobe of the tail, or, in the language of M. Agassiz, they are less hetero- 

 cercal. The teeth also, according to Sir P. Egerton, who, in 1 844, 

 examined for me a fine series of specimens which I procured at Durham, 

 Connecticut, differ froni those of Palceoniscus in being strong and conical. 



That the sandstones containing these fish are of older date than the 

 coal-bearing strata near Richmond in Virginia, which have been shown 

 (p. 451) to be about the age of the European Keuper, is probable. 

 The high antiquity of the Connecticut beds cannot be proved by direct 

 superposition, but may be presumed from the general structure of the 

 country. That structure proves them to be newer than the movements 

 to which the Appalachian or Alleghany chain owes its flexures, and 

 this chain includes the ancient or palaeozoic coal-formation among its 



* Journal of Voyage of Beagle, &c., 2d edit., p. 89 ; 1845. 



