Professor Emerson on HalVs Geological Collections. bib 



IIG. Dolomite. 



A compact buif magnesian limestone, effervescing veiy slowly with acid. 

 Upper Silurian. ? Kiid-lu-nann. 



117. Dolomite. 



A yellowish white, very compact and tough rock, without fossils. 

 Frobisher Bay. 



118. Dolomite. 



A pale cream-colored magnesian limestone, compact, fine-grained, breaking 

 with very flat, broad .conchoidal fracture, extremely brittle and ringing sharply 

 under the hammer, only slightly whitened by weathering. Several large pieces 

 were present, all uniformly and abundantly filled with the minute tubular cavities 

 mentioned on page 579. 



Locality, "Hall's Island of Frobisher." 



119. Dolomite. 



Many fragments of gray and buff limestones, all probably magnesian. 

 French Head, Field Bay. 



DESCRIPTION OF FOSSILS. 



The fossils described below belong for the most part to two horizons. That 

 of the Utica slate in flinty bituminous limestones, and that of the Trenton, rich 

 in entomostraca, in gray argillaceous limestone. 

 BuTHOTREPHis, conf. gracilis, Hall. Fig. 1. Natural size. - ^ 



Stem stout, subcylindrical surface rough, succulent, ? (k>f z' \ ' / 

 branching. Branches alternate acuminate. • ■ '^ 



A unique specimen upon the surface of a piece of com- 

 pact gray limestone like that containing entomostraca. The -^ .. „ >^ 

 stems stand out from the surface of the rock, and are of 



lighter color and rougher than the rest of the surface of the rock. At one place 

 alternating rounded stems, having a fruit-like aspect, are present, and many short 

 separated branches are scattered over the surface. 

 Protozoa. 



A small fragment of weathered silicious limestone, black at center, gray 

 externally, shows many curious forms, which seem to be sponge spicules and tests 

 of silicious protozoa. What appears to be a hexactinellid spicule is repeated 

 several times, four hollow tapering tubes, radiating at right angles from a com- 

 mon center, with which the cavities of the tubes are continuous, and in which one 

 looks down into the cavity of a fifth tube, the sixth having been removed in 

 cutting the section. Also many fragments, pierced with close-set hexagonal open- 



