104 



OHIO FOSSILS 



Fig. 271 



TRILOBITA . These are rare in our Mississippian rocks. Brachymetopus 

 rusticus (fig. 271) is a small species in which both the head and tail are 

 ornamented with numerous bumps and short spines. Heads are very rare but 

 tails in fair numbers have been found in some beds of the Logan. 



Griffithide s marginatus (fig. 272) has only low bumps instead of bumps 

 and spines. The tail is proportionally narrower than that of Brachymetopu s 

 rusticus . Tails of G. marginatus are found sparingly in parts of the Logan. 



Fig. 272 



ECHINODE RMA . Crinoid stems are common in some of the Mississip- 

 pian beds in northern Ohio. Crinoid heads are extremely rare. Hall and 

 Whitfield (1875) have described the Ohio species. The other classes of 

 echinoderms occur too rarely for mention. 



FISHES . Scales and plates of fishes turn up fairly frequently in our Mississippian 

 formations, especially in the black shales, but few identifiable remains may be expected. For 

 discussion of some Mississippian fishes, see chapter 2, p. 22 . Newberry (1873, 1875, 1889) 

 has described most of our species. 



Books for further study 



Hyde's work (1953) is the most useful source book for the Mississippian invertebrates of 

 southern Ohio. It contains descriptions and figures of most of the common forms and it is 

 recent enough to be still available. Many Mississippian species are described in Hall and 

 Whitfield's (1875) report on the Waverly fossils of northern Ohio. That volume is now out of 

 print but is available in libraries. Morse's (1910) work on the Maxville limestone, Bulletin 

 13 of the Geological Survey of Ohio, and his (1911) paper on the fauna of the same formation are 

 also useful. 



