358 



PROCEEDINGS OF THE GEOLOGICAL SOCIETY. 



(Hall, Pal. ii. 83) ; there is not one of either west of Rochester : 

 the shales below the iron-ore bed on the east side of Wolcott have 

 chiefly furnished them, while one or two species are common further 

 east in the non- calcareous strata. More may be expected, and would 

 probably have been found, but from the low and marshy nature of the 

 country thereabouts. Perhaps Tellinomya machceriformis is the most 

 plentiful bivalve in the group. 



Trilobites are not prominent, and in many places are wanting. 

 Nine new ones, nevertheless, appear in the west, under Wenlock 

 influences ; two have been derived, and four transmitted, leaving six 

 to remain typical. These are mostly verv unlike each other (Hall, 

 Pal. ii. 296). 



We rarely find entire trilobites east of the Genesee River. From 

 this line westward to Lockport there is a constantly-increasing num- 

 ber of individuals, and a greater perfection in the specimens obtained. 

 From this circumstance, and from the fact that in the west part of 

 the State crinoids flourished in great numbers at the same time, we 

 may infer that many of the fragments (mostly bucklers and caudal 

 shields of trilobites) found in the thinning eastern extension of the 

 shale have been drifted from localities further west. 



Of the Gasteropoda eight are original, one received, two trans- 

 mitted, and seven are left typical (see Table No. II.). The Gastero- 

 poda are confined to that part of the Clinton group (Hall, Pal. ii. 

 83), which is east of Genesee River ; and many of them occur as 

 casts in ferruginous shaly sandstone. 



Evidently physical conditions have here had much to do with the 

 number and kind of Cephalopoda. Eleven are original, two received, 

 three transmitted, and eight are typical, — here repeating the lesson 

 often presented by the comparative incapacity of groups of sediments, 

 or successive sea-beds, to receive and nourish each other's population ; 

 and this partly perhaps because in New York the floras of the feeding- 

 grounds are respectively restricted always to a single group. 



Some interesting Cephalopoda are nearly confined to the lower 

 part of the Clinton group. 



The most remarkable genus is the Ormoceras, of which a single 

 species, O. vertebratum, occurs in great numbers in Chazy Lime- 

 stone : it is rare in Trenton Limestone, appears again in the Hudson- 

 River-group, and then lastly in the Clinton, having been formerly 

 thought typical of the lower stage. It doubtless owed its strong 

 viability to its free powers of locomotion. 



Fossils occurrent in Europe. — Fucoides gracilis ; Cornulites serpularius ; 

 Halysites catenulatus ; Favosites gothlandica ; Fenestella prisca ; Glyptaster 

 brachiatus ; Atrypa hemisphaerica ; A. reticularis ; Leptaena corrugata ; L. 

 depressa; L. sericea; Pentamerus oblongus; Spirifer lynx; S. radiatus; 

 Beyrichia lata; Calymene Blumenbachii ; C. punctata; Phacops sphae- 

 rexochus (18). 



Fossils recurrent in New York. — Halysites catenulatus ; Rhinopora ver- 

 rucosa ; Trematopora tubulosa ; Caryocrinites ornatus ; Glyptaster brachia- 

 tus ; Hypanthocrinus decorus ; Leptaena crenistria (Devonian also) ; L. 

 depressa ; L. obscura; Orthis elegantula; Spirifer radiatus ; Atrypa ema- 

 cerata (Devonian also); A. neglecta; A. reticularis; Avicula emacerata; 



