Organic Siliceous Remains. 243 



5. M. everefcti, Potts and Mills. 



6. Heteromeyenia ryderi, Potts. 



7. H. argyrosperma, Potts. 



8. H. pictovensie, Potts. 



9. Tubella pennsylvanica, Potts. 



The first of these was described by Bowerbank as S.lordii. The 

 specimen came from British Columbia. ] t was first discovered 

 in England last summer, according to Carter. It turned out on 

 examination, that Leidy, of Philadelphia, first described it as S. 

 fragilis. No. 2 was described by Bowerbank over twenty years ago 

 as S. dawsoni ; next, by Potts as S. lacustroides. I called 

 Mr. Potts' attention to Bowerbank' s description, and it has been 

 generally conceded since to be an American variety of the Euro- 

 pean S. lacustris. No. 3 was described by Carter, of England, in 

 the January number of the ''Annals and Magazine of Natural 

 History," London. Potts claims that it is the same as his S. 

 iglooi/ormis, a description of which, we think, has not yet been 

 published. No. 5 is remarkable, as the species has never been 

 observed before except in a pond upon Mt. Everett in Mass., 

 U.S.A., at an elevation of 1,8'<»0 or 2,U00 feet above the sea. It 

 appears to be plentiful in Nova Scotia. No. 8, provisionally named, 

 is remarkable for the paucity of its statoblasts, which for some 

 time prevented its classification, although its skeletal spicules are 

 very distinctive. Further investigation is necessary for the elucida- 

 tion of the character and life-history of this species. This 

 classification and nomenclature has tue approval of H. J. Carter, 

 the greatest living English writer on sponges. 



E. Potts of Philadelphia, our best American authority, has 

 observed that the spicules of sponges undergo variations within a 

 very considerable limit, and that these variations are generally 

 concomitant with the variation of the altitude of their habitat. 

 The spicules of several of these Nova Scotian sponges he con- 

 siders as varying from the usual type, but considers them as con- 

 forming to his hypothesis. The extensive deposits of these 

 siliceous remains must have come proximately from silica in 

 solution in the water. The analysis of the waters of Halifax 

 lakes by Prof. Lawson shows the presence of soluble silica as well 

 as of alumina, lime and iron, ail of which have been found to 

 exist in diatomaceous earths analysed by Zeigler, Hoffman, and 



