306 APPENDIX 



Hydroids allied to the Hydractiniae and Millepores.^ 

 I confess that I am not satisfied with these inter- 

 pretations. I have in my collections large numbers 

 of encrusting spinous forms, usually called Stroma- 

 toporae, but which I have long set aside as probably 

 Hydractiniae. There are other forms with large 

 vertical tubes which I have regarded as corals, but 

 some Stromatoporae seem to be different from either, 

 and I am still disposed to regard many of them as 

 Protozoa. Bearing in mind, however, that the 

 Silurian is as remote from the Laurentian on the 

 one hand as from the Tertiary on the other, we 

 might be prepared to expect that if the Layer-corals 

 of the Silurian are divisible into different groups, 

 somewhat widely separated, and we have in the 

 lower Palaeozoic the peculiar type of Cryptozoon, 

 we may be prepared to expect in the Laurentian 

 much more generalized forms, less susceptible of 

 classification in our modern systems. If, therefore, 

 Eozoon were accessible to us in a living state, I 

 should not be surprised to find that — while perhaps 

 more akin to the calcareous-shelled Rhizopods than 

 to any other modern group — it may have presented 



^ See Nicholson and Murie's able memoirs, Publications of 

 Pal. Soc, 1885. 



