3o6 Ulrich on Correlaiton of the Lo-tvcr Siluricn. 
Total No. sp. mentioned from beds Xlb 1.36; restricted to same, 41 
' " " XII 199; •' " 113 
" Xlla 142; " " 57 
" Xllb 121; " " 46 
" XIll 141; " " 60 
" XIV 91; " " 27 
Species common to XIa and Xlb 80 
" Xlla " Xllb 58 
XI " XII 52 
"XII " XIII 46 
" XIII " XIV 57 
Total No. of species passing from beds XIa into and not beyond Xlb 37 
XI " " " XII 20 
XI " " " Xlil 7 
" " " " " XI into XIV 24 
" " " " " Xlla into and not beyond Xllb 24 
XII " " " XIII 30 
XII into XIV 30 
" " " ranging through all tbe beds from XIa to XIV, 23 (2 doubtful) 
" " " passing up from lower beds andranging through 18 
" " " " " " '• into beds XI or higher, 58 (4doubtful) 
Of these 58 species 22 are not known above beds XI 
3 occur in beds XT but are last met with in beds XII 
3 " '• A'/ and A'i/ but are last met with in beds XIII 
6 " " A// but are not known in beds Xl,Xlll,XlV 
1 occurs " AT/// and A'/ T but is not known in beds A'/ and A// 
1 " " AiF but is not known in beds A'/, A'i/, and A/// 
We will now proceed to consider these beds more in detail. 
Beds XI. This division is about 300 feet thick at Cincinnati, 
Ohio, and consists mainly of shales separated at intervals varv- 
ing between 2 inches and 6 feet, by mostly thin layers of lime- 
stone. The latter vary in thickness from i to 24 in., yet are 
rarely more than 6 in., and commonly less than 4 in. In gen- 
eral terms they may be described as drab to bluish, sub-crystal- 
ine, even bedded, firm limestones, usually charged \\\\\\ fossils. 
The drab courses are somewhat sandy and in them fossils are 
rather scarce. 
The shales vary both in color and firmness, those met with in 
the lower portion of the division being harder and their bluish 
tint less decided than that of those which constitute the bulk of 
the middle and upper portions of the section. 
These beds as they are exposed in the vicinity of Cincinnati, 
admit of being again divided into two subdivisions, which may 
be designated, as a and b. In the following careful description of 
their peculiarities, I shall endeavor to show that they are dis- 
85 « Lichcnocriuus crateriformis Hall in columns L. B, xi «, and xi ^; 
87 also in xi b\ 91 and 92 range up from column L. B; add as 121a He- 
terotiypaf vaupelt, in xii b; 126 occurs in xi 6-, xi b and xii a\ 203 also in 
xiii; 240 occurs apparently only near top of xii a, and not in xii b\ 245 
should read G. sckucJierfaiia Ulrich; 266 and 297 also in xii a\ 311 also in 
XIV ; 328 in xii instead of xiv; 362 in xi b instead of xii a\ 391 in xii ^ in- 
stead of XII ;« 395 also in xiii; 442 and 443 in xii b instead of xiii;444 in 
XII a instead of xii b; 448 in L. B. and xi a. 
