

BIGSBY — PALAEOZOIC ROCKS OF NEW YORK. 367 



Vanuxem find in the second deposit some Cytherince, about half the 

 size of those in the next groups above and below. They occur in 

 a thin layer of calciferous slate, which makes a large portion of the 

 third deposit (Vanux. p. 98). 



Both the Onondaga and Tentaculite Limestone contain the Eury- 

 pterus remipes, in clayey limestone with gypsum, in the upper range, 

 third deposit, near Waterville, — at the end, therefore, of muddy 

 saline deposits, on the reappearance of a purer lime. 



I am not aware of the presence of a Trilobite in this group. We 

 find in the top and bottom of the Onondaga-Salt group twenty-one new 

 forms, chiefly Gasteropoda, — and these principally in its highest 

 calcareous strata, and having a strong Devonian facies. 



Eight species have been received from other Silurian epochs. 

 They are — 



Chsetetes gothlandica, Stromatopora concentrica, Leptsena obscura, L. 

 subplana, Avicnla rhornboidea, Orthoceras aequale, Cornulites serpularius, 

 Tentaculites ornatus. 



Two only are transmitted onwards, while twenty-two are typical; 

 almost wholly Gasteropoda and Cephalopoda. 



This group has few affinities with any other deposit. The Gait 

 fossils (Upper Canada), which have so added to the fauna of the 

 Onondaga-Salt group, will perhaps prove to be Devonian (Onondaga 

 Limestone, see p. 375). The region in which they were found has 

 not been properly examined. 



Fossils typical. — Of the twenty-two typical fossils, fourteen were 

 unexpectedly discovered at Gait in Upper Canada, about sixteen 

 miles to the N.W. of Lake Ontario, in a white limestone (Hall, Pal. 

 ii. 147). The typical fossils, by name, are — 



Heliolites interstincta, Pentamerus occidentalis (Gait) ; Megalomus cana- 

 densis (Gait) ; Avicula triquetra; Cyclonema sulcata ; Murchisonia bivittata 

 (Gait) ; M. Boydii (Gait) ; M. Logani (Gait) ; M. longispira (Gait) ; M. ma- 

 crospira (Gait) ; M. turritiformis (Gait) ; Pleurotomaria bispiralis (Gait) ; P. 

 perlata (Gait) ; P. sp. ind. (Gait) ; P. solaroides (Gait) -, Subulites ventricosa 

 (Gait) ; Cyrtoceras arcticameratum ; Orthoceras laeve ; Cornulites, sp. ind. ; 

 Calymene, sp. ind. ; Hypanthocrinites ornatus ?, De Verneuil. 



Fossils occurrent in Europe. — We only know three — Tentaculites 

 ornatus (a Middle and Upper Silurian in both hemispheres), Favosites 

 gothlandica, and the Atrypa didyma, detected by Daniel Sharpe in 

 Sir Charles Ly ell's collection of American fossils. 



Fossils recurrent in New York. — These have been already enume- 

 rated, and are derived from the two groups nearest below, except the 

 Orthoceras cequale (a swimmer), also occurring in the Utica Slate 

 and the Hudson-River group in the E. of New York, where these 

 come in contact with the Onondaga-Salt group. 



Waterlime Group. 



Mineral Character. — It is composed of two principal members, — 

 Water-limestone and Tentaculite-limestone. Each of these, says 

 Hall, should be subdivided. 



