382 PROCEEDINGS OF THE GEOLOGICAL, SOCIETY. 



culling them from the dried ocean-mud, so much do these soft shales 

 resemble the mud-deposits on the bays and shores along the sea- 

 side. It is so rich because its mineral character undergoes constant 

 variation. In the east of New York, many of the fossils of this group 

 enter the Chemung, their lithology being there much the same, which 

 is not the case further west and south-west. 



James Hall, in 1854, expected to find in the Hamilton, Portage, 

 and Chemung groups 300 species, — or double that number, if the 

 investigation were pursued in the Western Counties as well as in New 

 York. They are at present known to be 155. 



In the east of New York, this group abounds with Avicula (14 

 species out of 33, New York Devonian), Cypricardia (14 out of the 

 20, Devonian), and Nucula (10 out of 12, Devonian), — while at the 

 west end of the State they are very rare, and are replaced by abun- 

 dance of Spiriferi and Atrypce ; and this from change of habitat. 

 Some of the more abundant Corals of Marcellus Shale are here, — new 

 forms, however, being plentiful, and vastly so the Brachiopoda and 

 Dimyaria. 



We have here 127 creations or new appearances. Among these are 

 47 Brachiopoda. There are 22 Monomyaria, 30 Dimyaria, 5 Trilo- 

 bites, 11 Gasteropoda, and 6 Zoophyta (see Tables VII. and VIII.). 



A terrestrial plant has been found in this group, near Cooper's 

 Town ; its first appearance in the New York Basin (Hall). 



There are marine plants also ; but they have not been described, 

 except the singular Fucoides Caudagalli. The genera of some of the 

 Corals, Molluscs, and Trilobites are the same as those in the Niagara 

 group : but this would seem to prove little ; for the genus Tellina 

 appears to run through ten formations, from Upper Silurian to the 

 recent period, and the genus Cardium through twenty-two (Morris). 



A ridged Posidonomya is found on both sides of Lake Otsego. 

 The Acephala are many and fine. Agelacrinites Hamiltonius is said 

 to have been found at Hamilton (Vanuxem) . In North America there 

 are several species of this curious animal (according to Mr. Billings, 

 the palaeontologist of the Canadian Geological Survey), one of which, 

 the A. Buchii, was found by me many years ago in Trenton Limestone 

 at Hull, near Ottawa, Upper Canada. We have Goniatites punctatus, 

 and the first New York Inoceramus (oviformis). An Asterias from 

 this group is quite different from those of the Lower Silurian stage, 

 or of the present seas, in having the plates perforated by pores, the 

 pores not passing between the plates (Hall). 



This group was evidently produced in quiet times. There were no 

 disturbances, uplifts, currents, or high waves. The deposit was 

 made too deep to be reached by surface-waves, except perhaps in 

 particular places (Hall). Its muddy bottom suited the Lamellibran- 

 chiata well. 



Some beds of limestone in the middle of the Hamilton group are 

 entirely filled, on Lake Skeneateles, with Cystiphyllum and Cyatho- 

 phyllum (Hall). 



The same group of fossils is often maintained exclusively for many 

 miles, as on the south shore of Lake Erie, where there is a thin stra- 



