182 WALKS AND TALKS. 



like a potato, roundish or oblong, and is covered all over with 

 small cell-mouths which are nearly circular in outline, but often 

 angular, from mutual crowding. When one of these coral 

 potatoes is split open-, and one surface polished, the tubes 

 which run down from the surface can be beautifully seen as 

 also the transverse divisions or tabukz, and the perforations or 

 pores along the outer walls of the tubes. 



It is quite wonderful to see the number of parasitic crea- 

 tures which attached themselves to these and other corals. The 

 surface of Acervularia was sometimes a whole world. Here is 

 a little bivalve shell spreading its fibrous rootlets out to make 

 itself secure (Crania). Here are numerous little coiled shells 

 (Ser'pula) of the class of Worms. Here is a little coral con- 

 sisting of a branching chain of cornet-shaped tubelets attached 

 with the small end of each to the under side of its predecessor, 

 near the upturned aperture (Au-lop'-o-rd). There are half a 

 dozen species of these. One aggregated itself in dense, thick 

 masses. One was beautifully small and delicate. One was 

 extremely fine, almost like a spider's web trailing over the sur- 

 face really a distinct genus. Then we find patches an inch 

 in diameter and less, which look like films of varnish pricked 

 full of pin-holes at equal distances. There are coaser and finer 

 sorts (Fis-tu-lip'-o-ra and Gal-lop' -o-r a). Another incrusting 

 coral is like excessively fine lace (Mon-tic-u-lip'-o-ra). There 

 are many other attached organisms of less frequent occurrence. 

 I hope readers who visit Petoskey will take pains to look up 

 these interesting forms and learn their names. Petoskey is not 

 by any means the only region where most of them occur. At 

 Thunder Bay, on Partridge Point, is an amazing quantity of 

 delicate coral structures composed mostly of little bars, slightly 

 divergent, lying in one plane, and having cross-connections, 

 forming a structure in some cases like woven cloth, with open 

 meshes. One finds an amazing number of variations in de- 

 tails. I have picked out from this locality alone one hundred 

 different species of these (Fe-nes-tel'-li-dce) and related forms 

 (all Bry-o-zo'-ans). Then, at Widder in Ontario, we find a 

 regular bank of bivalve shells of a certain species (Spi-rif-e-ra 



