FAUNAS OF SOUTHEASTERN ALASKA 323 
These crustaceans comprise the fauna of the lower 700 feet of the 
section, so far as discovered. 
In the upper 300 feet of the limestones of the section a crustacean 
fauna also predominates, but the types represented are unlike those 
of the preceding division. One of the conspicuous forms in this 
fauna is a large undescribed ostracod provisionally referred to Iso- 
chilina by E. O. Ulrich, having a length of 14 inches. Fragmentary 
specimens indicate the presence of one or more other species of large 
ostracods, which together 
with a new species of 
Ceratiacaris are associ- 
ated with the large [so- 
chilina. Other forms 
occurring in this portion 
Ole athe: ssec tiom, ate 
Zaphrentis? sp., repre- 
sented: bya, single 
specimen, Meristella 
tumida Dalm.? and 
Megalomus sp. undt. 
The Megalomus is a 
‘large and very thick- 
shelled bivalve com- 
parable in this respect 
with Megalomus cana- 
densis of the Guelph, 
and identical with a 
species occurring in the 
limestone at Glacier Bay. 
While none of the forms occurring in the two lowest divisions of 
this section have been identified with known species, the dominance 
of the large ostracods and the massive-shelled Megalomus and thick- 
shelled Murchisonias point to a late Silurian age of the fauna. The 
horizon represented is apparently about that of the Guelph. 
The Silurian fauna of Freshwater Bay is found also at Glacier 
Bay, to the northwest. A small collection in the National Museum 
made by Cushman, and a much larger collection by Mr. F. E. Wright, 
Fic. 2-—Upper Carboniferous limestone, 
Hamilton Bay, Kupreanof Island. 
