156 NEW YORK STATE MUSEUM 



part of the length of the sea wall the strata are essentially vertical 

 with slight undulations; but at a distance of about 250 feet from the 

 south end of the cliff the strata become much more irregular, main- 

 taining their essentially vertical attitude but are folded and slightly 

 displaced among themselves and faulted against the more erect 

 strata of the main part of the mountain. The southern part of the 

 mass is composed of strata similar to those of the northern but in- 

 creasingly slaty in composition. In both parts of this Mt Joli mas- 

 sive fossils were found, but they are by no means of common 

 occurrence ; moreover they are wedged in the vertical strata so that 

 their extraction is not easily accomplished. From their calcareous 

 layers, which with the eroded interleaved shales form the outermost 

 northern reach of the strata and are exposed only at low tide as reefs, 

 were obtained a few fossils : Platyceras, large species of Helderberg 

 type ; Zaphrentis corticata Billings ; Z. c i n g u 1 o s a 

 Billings. 



The shaly layers on the high vertical north face of the scarp have 

 afforded species provisionally identified as follows : 



1 Hindia sp. ' 8 Stropheodonta cf. varistriata Con- 



2 Monograptus cf. clintonensis Hall rad 



3 Duncanella cf. borealis Nich. 9 Spirifer cf. niagarensis Conrad 



4 Streptelasma cf. caliculus Hall 10 Spirifer modestus Hall? 



5 Michelinia cf. lenticularis Hall 11 Cypricardinia aff. sublamellosa 



6 Dalmanella cf. perelegans Hall Hall 



7 Leplaena rhomboidalis Wilckens 12 Phacops sp. 



Giving special attention to the trilobite in which lies the clearest 

 indication of geologic age, we- find it to be a fully developed Phacops 

 such as nowhere occurs in the typical Siluric deposits of the Missis- 

 sippian sea or Appalachian gulf. Its glabella is large, rotund and 

 coarsely pustulose, the glabellar furrows obsolete, eyes large and the ; 

 genal angles have minute spinules. The pygidium is broad, the axis 

 having six to eight well defined rings, the first bearing a prominent 

 tubercle, the pleurae having five to six ribs all grooved and separated 

 by deep furrows. These structural points indicate an early period in 

 the history of the genus, hence if Siluric, a final stage. The species 

 is equivalent to Phacops logani of the Helderberg and 

 Oriskany of New York, of the Perce rock and the Grande Greve 

 limestones. 



