^ingueberg on the Niagara Shales. 371 
thus far been found. Some magnificent ones with a goodly 
proportion of the column and arms intact have been secured. 
This species makes its first appearance in the Clinton, where it 
is very rare, passes through the Niagara Transition, appears 
in slightly increased numbers, rapidly augments its ranks and 
reaches its maximum in the upper portion of the lower third; 
extends in moderate numbers up into the middle third, before 
leaving which it rapidly subsides, being almost unknown in the 
higher portions of the upper third. After a temporary emi- 
gration to more favorable haunts it returned and is again found 
in the limestones immediately above; after which time it prob- 
ably became extinct. Coincident with the preceding is the rise 
and fall of Dalmanites. 
Here also are found the best examples of Myelodactytus hrach- 
latiis which, though rare, occui's uniformity through the loiver 
third. 
The middle third. This and the divisions following are de- 
fined by the negative evidence afforded by the absence of many 
species. A few exceptions may be made, the most prominent 
being the development of Honialonatus which reaches its max- 
imum size after leaving the Homocrinus band, and extends up- 
ward though in diminished numbers into the highest fossiliferous 
beds of the upper third. A more careful stratigraphic classifi- 
cation may yield some species of polyzoa which will be found 
peculiar to it; thus the rare Clathropora frondosa has as yet 
only been found in its upper portion, and possibly extends into 
the third aboAC. Striatopora Jicxuosa is found here, and but 
rarely elsewhere. The few sjoecimens of Cornulites and Sto- 
matopora are mostly from within its borders as is also the case 
with Tentaculitcs niagarcnsis and its almost universal asso- 
ciate Beyrichia spinosa and the rarer B. symmetrica which are 
mostly from its upper part. This latter trio extends into the 
upper third. The types l^ubcrciilopora iiiflata., Crania pan- 
nosa., C. dentata and C gracilis occur here. The only other 
Crania known from the shales is a species which I have consid- 
ered as identical with C siluriana, which has only been foimd 
in the loxvcr third. Callocystites tripcctinatus also occiu's here. 
The most notable absentees are among the crinoids and 
cystids referred to as peculiar to the loiver third. After these 
come the brachiopods which have before been listed. 
