82 



OHIO FOSSILS 



Fig.m 



Leiorhynchus (fig. 171) is similar to Camarotoechia but the central ribs, 

 those on the fold and sinus, are larger than the side ones which may be lacking. 

 Several species occur in our Devonian. 



Schizophoria is a neat shell of medium size with a weak fold and sinus, 

 practically absent in some specimens. S_. propinqua 

 (fig. 172) is found in the Columbus limestone and similar 

 species in the Olentangy and Plum Brook shales, the 

 Silica formation, and the Prout limestone. 



Elytha ( Reticulari a, Delthyris , and Spirifer f imbria ta 

 of older publications) is distinguished by its fine spines 

 which may look more like fine radiating markings in 

 poorly preserved specimens. E. f imbriata (fig. 173) occurs 

 in the Columbus and Prout limestones. 



Cyrtina has the general appearance of Spirifer but is character- 

 ized by having one large beak and a correspondingly large triangular 

 area under it. Most of the Spirifers also have a triangular area 

 under the beak but it is smaller than that of Cyrtin a. C. 

 hamiltonensis (fig. 174) is found in our Devonian. 



Fig. 173 



Spirife r is distinguished by its characteristic form: 

 in side view each valve suggests a butterfly with pointed 

 outspread wings. The genus contains a great many species 

 (figs. 175-181) which have been split up among several 

 comparatively new genera. Strictly speaking, there are no 

 true Spirifers in the Devonian; all our species have been 

 transferred to other genera. We have kept the group together here since it is more easily 

 understood than the finer genera. About 10 species are common in our Devonian rocks. 



Rhipidomell a has already been described in the Silurian chapter (fig. 113). Comparison 

 of figure 113 with that for Atryp a (fig. 182) will easily separate the two genera. R. vanuxemi 

 occurs in the Columbus, Delaware, and Silica. 



Atryp a (fig. 182) is another genus found in both the Silurian and Devonian. Some older 

 records lump most Atrypas as A. reticulari s, a Silurian species, but recent workers separate 

 the Devonian forms as distinct species. 



Chonetes (fig. 183) is a small brachiopod, often abundant on slabs of Devonian limestone 

 and shale. Its small size is distinctive. Many species are found in our Devonian. 



Schuchertella (see fig. 253) is very similar to the next three genera but has a smooth 

 hinge line whereas the next three have tooth-like projections on the hinge. Three species 

 are common in our Devonian. 



Stropheodonta (fig. 184) has teeth on the entire hinge and its riblets are of more or less 

 equal size. Several species are common in our Devonian. 



Megastrophia (fig. 185) is like Stropheodonta but its riblets are arranged in a character- 

 istic pattern, two large ones with many smaller ones between them. M. hemisphaerica occurs 

 in the Columbus and Delaware. 



--<ii»-' 



Fig. 174 



PELECYPODA. 



Fossil clams and scallops are scarce in our Devonian rocks as compared 

 Only Conocardium can be called fairly common and it may not be a 



with the brachiopods. 



pelecypod at all. It appears twice in the key because some species fit both choices given in a 



