92 



OHIO FOSSILS 



6. a 

 b 



7. a 

 b 



8. a 

 b 



9. a 



b 



10. a 

 b 



11. a 

 b 



Front margin of head fluted Odontocephalus 



Front margin of head not fluted Coronura 



Tail 

 Tail 



without spines 8 



with spines 10 



Tail *vith a distinct border Proetus 



Tail without border 9 



Tail with a tubercle on the center of each segment Trypaulites 



Tail segments without central tubercle Phacops 



Tail with a long terminal spine Anchiopsis 



Tail without terminal spine but with 2 or more side spines 11 



Two short side spines only Odontocephalus 



Many short side spines, two on almost every segment Coronura 



Phacops (fig. 224) is the only genus which has neither cheek nor 

 tail spines. The central part of the head bulges out in front and the 

 tail lacks the border of Proetus . A complete specimen of P. ranamill - 

 eri from the Silica formation is shown, much enlarged, on the frontis- 

 piece of this book. 



Proetus has cheek spines but no tail spines. 



Fig. 225 



Fig. 224- 



The central part of the head bulges out in the back. The tail has a distinct 

 border. P. rowii (fig. 225) is found in the Columbus, Delaware and Prout. 



Trypaulites (Chasmops in older publications) has cheek spines but 

 no tail spines. The central part of the head 

 bulges out in front but is not lobed, and there is 

 no central neck spine on the head. The tail is 

 without border or spines but has a tubercle in 

 the central part of each segment. T. calypso 

 (fig. 226) occurs in the Columbus. 



Fig. 226 



Anchiopsis has cheek spines, a central 

 neck spine, and a terminal tail spine. Some specimens are quite large, 

 but not as large as Coronura . A. anchiops (fig. 227) is found in the 

 Columbus. 



Fig. 227 



Odontocephalus (fig. 228) has cheek spines but 

 no central neck spine. The two tail spines are on 

 the sides, not terminal. The central part of the head 

 is lobed and bulges out in front. The flutings on the 

 front of the head are distinctive. Two species occur 

 in the Columbus. 



Fig. 228 



Coronura (fig. 229) grows very large; it is the largest of our 

 Devonian trilobites. It has cheek spines but no central neck spine. The central part of the 



