APPENDIX 



313 



fragments in Silurian and Carboniferous and Jurassic 

 limestones in England. ^ 



The Streptochetus of Seely from the Chazy lime- 

 stone 2 is evidently very near to Girvanella, if not 

 generically identical, and I have a similar species 

 from the Lower Cambrian pebbles in the con- 

 glomerates of the Quebec group. In all these 

 forms, however, the thicker or intermediate laminae 

 seem to consist wholly of definite convoluted tubes, 

 whereas in Cryptozoon the tubes, or tubular per- 

 forations, are separated by a mass of material which 

 in the best preserved specimens seems to consist of 

 a fibrous stroma including calcareous and silicious 

 particles. It seems doubtful to what class of beings 

 such a structure should be referred ; but whatever 

 its nature, it evidently had great powers of growth, 

 and seems to be a >^ery ancient form of life. 



One of the species similar \n structure to Hall's 

 type, but budding out into turbinate branches, was 

 discovered by Mr. E. T. Chambers, of Montreal, in 

 the Ordovician limestone of Lake St. John, and has 

 been named C. boreale. It differs in structure from 

 Hall's species in having the tubes less tortuous 



^ British Association, Liverpool meeting, 1896. 

 •^ Amer. Journ. of Science. 1885. See Nicholson, "Manual 

 of Palagontology," ed. of 1889. 



