32 



Fossils of the TJtica Slate. 







Thorax. 



ds of 











'Head, 

 based 

 limetre . 





Q 







grees of Development. 





imber of Segments in the 



< 

 a 



CO 



a 



a 



ti . 



1 ^ 



ngth of entire individual 



ngth of Head. 



ngth of Thorax. 



g 



be 

 Ph 

 o 



a 



Relative proportions ol 

 Thorax and Pygidium 

 on dividing the mill 

 into 16 parts. 



mber of examples in C. 

 alcott's collection. 



. Hurlburt's collection. 



;ier collections. 



0) 









o 



o 





nu. 



Th. 



Po-. 







Q 









^^^^ 



mm. 



mm. 



mm. 



mm. 















1 





1 



5 



1.12 



.5625 



.0625 



.5000 



9 



1 



8 



3 



1 





2 





2 



5 



1.50 



.6865 



.1750 



.6250 



11 



3 



10 



4 







3 





3 



0—0 



2.00 



.8750 



.5000 



.6250 



14 



8 



10 



15 







4 





4 



0—0 



2.25 



1.0000 



.6250 



.6250 



16 



10 



10 



16 



, 2 





5 





5 



0—0 



2.50 



1.0000 



.8125 



.6875 



16 



13 



11 



17 



2 





6 





6 



0— o 



3.00 



1.1250 



1.1250 



.7500 



18 



18 



12 



3 



4 





7 





7 



ft 



0— D 



3.50 



1.3750 



1.3750 



.7500 



22 



22 



12 



9 



1 





8 





8 







4.00 



1.5000 



1.7500 



.7500 



24 



28 



12 



9 







9 





9 



5 



4.50 



1.7500 



2.0000 



.7500 



28 



32 



12 



3 



3 





10 





10 



5 



5.00 



1.8750 



2.2500 



.8750 



30 



36 



14 



7 



1 





11 





11 



5 



5.50 



2.0000 



2.6250 



.8750 



32 



42 



14 



3 



1 





12 





12 



5 



7.00 



2.5000 



3.7500 



.7500 



40 



60 



12 



3 







13 



min. 



13 



5 



7.00 



2.5000 



3.7500 



.7500 



40 



60 



12 



3 





3^ 



13 



max. 



13 



5 



24.00 



7.5000 



14.0000 



2.5000 



120 



224 



40 









14 



min. 



14 



5 



^7.00 



2.5000 



3.7500 



.7500 



40 



60 



12 



19 



5 



1' 



14 



max. 



14 



5 



30.00 



9.0000 



18.5000 



2.5000 



144 



296 



40 









15 



min. 



15 



5 



19.00 



5.5000 



11.5000 



2.0000 



88 



184 



32 







7^ 



15 



max. 



15 



5 



48.00 



12.0000 



31.0000 



5.0000 



192 



496 



80 







1^ 



16 



min. 



16 



5 



n6.50 



5.0000 



10.0000 



1.5000 



80 



160 



24 



" '2 





1' 



16 



max. 



16 



5 



53.00 



15.0000 



33.0000 



5.0000 



240 



528 



80 































116 



20 



13 



Orxamentation. 



The characteristic and only ornament is the spine which occurs 

 upon the centre of each segment of the thorax, the occipital segment 

 and the anterior segments of the pygidium. It is to be seen from 

 the first degree as at present known to the sixteenth. Upon the 

 thoracic segments of the adult of the latter degree, the spine bends 



' From Cincinnati, Ohio, Mr. Dyer's collection. 



' N. T. State Museum collections, from N. T, State. 



' Geology of Canada, p. 202. 1863. 



* Prof. Hall considers this the most prominent character of this species, Pal. 

 N. r., I, p. 251. 



