Review of the New York Geological Reports. 367 



to this, occurs in abundance near high water of the Ohio at Cin- 

 cinnati- Orthis pectinella abounds, according to Dr. E. in the 

 Trenton limestone of Jefferson County. This fossil differs only 

 in size and the number of ribs from one found in the hills at 

 Cincinnati. It is also closely allied to O. callactis of the Cara- 

 doc of England ; the interval between the ribs is greater and the 

 ribs fewer in the callactis than the pectinella. 



The Orthis striatula cannot be distinguished from a small and 

 delicately ribbed shell found in great numbers in the lower part of 

 the hills of Cincinnati. Dr. E. informs us that it is as constant at 

 all the localities of the Trenton rock, which hare been examined, 

 as any fossil hitherto observed. Both the western and eastern 



fossil are hardly distinguishable from the O. canalis of the Car- 

 adoc. 



It is possible that several species have been confounded under 

 the name of the Strophomena alternata: as Dr. E. remarks, alter- 

 nate fine and coarse markings are possessed by more than one 

 species. A vast number of individuals, embracing four or five 

 distinct forms, are found in the hills on the Ohio between Cin- 

 cinnati and Madison, which have more or less of this character. 

 Several of the same occur also in Iowa and Wisconsin. 



Plate 107, p. 396, 

 Emmons's Report. 



6 



P Imrotomaria 



at Cincinnati. 



it Waterto 

 species fo 





