290 



PALAEOZOIC TIME — DEVONIAN AGE. 



The Chemung group in New York affords great numbers of 

 Aviculce, many Brachiopods, including broad-winged iSpirifers, and 

 some Producti, a huge Goniatite (four or five inches in diameter), and 

 rarely a Trilobite. 



Characteristic Species. 

 1. Plants. — Fig. 502, Sjihenopteris laxus, Upper Chemung beds ; Sagenaria 

 Chemungensis, from near Elmira, N.Y. ,• 503, Lepidodendron Vanuxemi, from 

 near Owego, N.Y. Species of Catamites have also been found. At St. John's, 

 New Brunswick, occur the following species, first described, with one exception, 

 by Dawson: — the Dadoxylon Ouangondianum (a Conifer), Catamites Transitionis 

 Goeppert, Aster ophyllites parvula, Sphenop>hyllum antiquum, Lycopodites Mal- 

 thewi, Cordaites Robbii, a Sphenojiteris, Cyclopteris Jacksoni, and others. The 

 Cyclopteris occurs also at Perry, Maine. 



Figs. 505-507. 



Fig. 505, Aviculopecten duplicatus; 506, Pteronites? ChemuDgensis; 507, Orthoceras 



Acicula. 



2. Animals. — Fig. 504, Atrypa Hystrix ; Fig. 505, Aviculopecte 

 Fig. 506, Pteronites ? Chemungensis ; Fig. 507, Orthoceras Acicula. 



duplicatus 



III. General Observations. 

 Geography. — The character of the beds — the shales that were 

 made from mud-beds and the shaly sandstones from sand-deposi- 

 tions — which spread over western and southern New York and 

 southwest along the Appalachian region, which become more shaly 

 to the western limit of the State and more sandy in the opposite 

 direction, tells nearly the same story with regard to the geography 

 of the continent as in the Hamilton period. The rocks were largely 

 shallow-water or sand-flat formations, as shown by the ripple-marks, 

 shrinkage-cracks, and oblique lamination ; and they therefore indi- 

 cate by their great thickness a subsidence during their progress to 

 a corresponding extent, and, further, that this subsidence or change 

 of level affected most the Appalachian region. The shallow sea 

 probably extended westward, forming sandy deposits over Ohio, 

 though of much less thickness than in New York. 



