this mass lies much above the Maclurea magna. * "i^ * It 

 occurs at Chazy Village, Watertown and other places." 



The fossil to which Professor Hall gave the provisional 

 name Stromatocei-iuvi has proved a good genus, and the early- 

 description still holds. Its characterization as a subhemis- 

 pherical mass often silicified, as an excrescence upon the sur- 

 face of the limestone, is strikingly characteristic. Its horizon is 

 so well fixed that it has become a guide to the Black River, and 

 its silicified mass has helped to distinguish the rock when all 

 other fossil forms have disappeared. The specific name ritgo- 

 sum was well chosen the wrinkly character of the laminae 

 usually accompanying the genus. 



The number of localities where the fossil is found has been 

 greatly increased. Along the islands south and through the 

 Valley of Champlain wherever the Black River appears there 

 the Stro>nalocerium finds a place. A most remarkable display 

 is found in a stratum of rock near two feet in thickness made up 

 wholly of Stromcitocei'ium and Coliimnaria on a little island 

 just off the shore of Ferrisburgh, Vt., known as Button Bay 

 Island. 



Though referred to in the original description as a coral its 

 systematic position in classification like so many other ancient 

 and extinct forms has remained somewhat in doubt. 



The existence of this form has seemed entirely unique, a 

 bubble on the crest of the sea of life, it appears, then as sud- 

 denly disappears. 



Yet this isolation of species is seeming, not real. Whatever 

 may be said of the notable mutation or sudden disappearance 

 of this form, a careful study of the underlying rocks will show 

 that an assumption of its sudden appearance is without founda- 

 tion. The Chazy rocks of Isle La Motte offer complete evi- 

 dence of the long time existence of the genus Stromatocerium ; 

 that the species rugosufn does not stand alone. Two well de- 

 fined species at least exist. Other forms for the present con- 

 sidered varietal may very likely be found to be really good 

 species. And more, there are other examples which suggest 

 close relationship to Stromatocei'iiim. 



