222 



TWENTIETH REPaRT ON THE STATE CABINET. 



TABLE 



Showing the Vertical Disti'ibution of the Genera of the Family of Grapto- 



litidcB. 



GENERA. 



a 



eS 



03 



o 



v 



S 

 o 



o 

 a 



H 



o 



.S 

 "'5 



a 

 o 



-4-> 



a 

 5 



• 

 » 



u 



* 

 * 



bD 



cS 

 'O 



a 

 o 



O 



W) 



•73 



"a 



w 



o 



bD 



<o 



'73 



w 



Ph 



« 



a 



o 



a 



» 



be 

 a 



a 



O 



s 



o 



1 



eJ 



. ^ Sub-ffenera Monoprion, eto 





» 

 « 

 « 



* 

 * 



* 

 * 

 » 



» 



* 



♦ 



* 





Graptolithus, Jsub-genus Diplograptus 













T)imAi^nfjRAPTTrs..... .... .••... 











* 

 * 

 * 

 * 

 * 

 * 

 * 

 * 



♦ 

















I)ENDR06RAPTTTS» .... ...... ... ...... ...... a... .... 



* 





CALLOftRAPTUS ..•••.......- ........ ...... .......... 





DiCTYONEjrA 







Ptilograptus...... ...» .... .... ...... ...... ..ii .».. 







Thamnograptus 







"Ra«!TRTTF.S .... ... ..... ......................... 







Inocau lis 











BXJTHOGRAPTCS 







* 



* 



• • 



. . 







Oldhamia ? » 











' 



' ' 









' 



,' 



The pre-eminence of the Quebec group, as the period of the greatest 

 development in the Graptolitidae, is shown in the above table. Of the 

 seventeen genera and sub-genera here enumerated, eleven are known in 

 this period ; while four genera, viz. Phyllograptzis, DendrograptuSj Callo- 

 graptus, and Ptilograptus, are not at present known in any higher position 

 than the Quebec group, though one of them occurs in the Potsdam sand- 

 stone. All those genera having the nearest relations with Graptolithus 

 proper occur in this group, and the species of that genus found in it are 

 more numerous than in all the subsequent formations, so far as at present 

 known. 



In addition to circumstances originally favorable to their development 

 and growth, the subsequent condition presented during the period of the 

 accumulation of the materials of the Quebec group, in Canada, seem to 

 have been equally favorable to the preservation of graptolites, and in no 

 other formation have they been found with all their parts so entire. 



